Proceedings of the Workshop on

Government of India Ministry of Water Resources

Proceedings of the Workshop on CONSERVATION OF WATER RESOURCES IN ANDAMAN & NICOBAR ISLANDS: ISSUES AND CHALLENGES

Selected Technical Papers from Workshop held at CARI, Port Blair, A & N Islands On March 27, 2014

Central Ground Water Board Eastern Region Kolkata

Proceedings of the Workshop on CONSERVATION OF WATER RESOURCES IN ANDAMAN & NICOBAR ISLANDS: ISSUES AND CHALLENGES

Selected Technical Papers from Workshop held at CARI, Port Blair, A & N Islands On March 27, 2014

Edited by Dr. Indranil Roy Central Ground Water Board Eastern Region, Kolkata

Government of India Ministry of Water Resources

Central Ground Water Board Eastern Region Kolkata

Disclaimer The views expressed in the papers are authors own and Central Ground Water Board does not hold any responsibility for the same.

FOREWORD Andaman & Nicobar Islands, the ocean locked group of islands, is at present facing a severe challenge to cope up with gradually diminishing water resource in the face of increased demand of water as a result of rising population and change in lifestyle. Erratic rainfall coupled with population pressure in terms of increased ground water withdrawal and deforestation is making water resources of these islands gradually unsustainable. Increased demand for fresh and potable water has resulted in an unprecedented scarcity of ground water, which is also translating to deterioration in ground water quality at places. I am glad that Central Ground Water Board, Eastern Region is organizing a one day workshop on “Conservation of Water Resources in Andaman & Nicobar Islands: Issues and Challenges” at Port Blair, Andaman & Nicobar Islands on 27 March, 2014, aimed at discussing important issues related to conservation of water resources in the UT of Andaman & Nicobar Islands. The objective of this workshop is to share knowledge and views of different water experts / stake holders / Govt. organizations / NGOs, Environmentalist on water resource security and sustainability with possible recommendations for conservation and preservation. I hope the deliberations of this workshop will help to finalize a realistic road-map for achieving the objective with active involvement of all agencies working in the water sector. The sincere efforts made by the team of officers of Central Ground Water Board, Eastern Region, Kolkata under supervision of Dr. Indranil Roy in organizing this event deserves appriciation. I am thankful to CARI for their help extended by providing the auditorium to conduct the workshop. I also extend my appreciation to all who, directly or indirectly, are associated with the event.

PREFACE Global resource statistics shows that all natural resources are fast decreasing. There is hue and cry in every parts of the world specially for water, which is the basic need for sustenance of life after air. Situation like groundwater scarcity mainly arose from overexploitation as a consequence of population explosion and mismanagement in the name of modernization with economics playing a pivotal role. An islandic condition such as Andaman & Nicobar Islands is more prone to such situation with its scanty resource. Moreover, the freshwater lenses are prone to contamination. Hence, a proper management policy is need of the day which will include development and effective utilization of water resources. Water Conservation and Resource Management is one such approach which identifies different independent uses of water and provides a framework of holistic water usage, confronting various sectoral interests. Each of the identified main water use sectors, i.e. Agriculture and Irrigation, Public Water Supply, Industry, Fisheries, Tourism, Energy, Transport, Wastewater, etc. has strong negative impact on water regime. The situation is worsened in by poor management practices, lack of regulation or lack of motivation due to the water governance regimes in place. Though, through out the world, Government considers water resources planning and management as core responsibility, but within government, water management responsibility is distributed across various agencies. This leads to responsibility conflict strongly dominated by sectoral interests. With this situation at hand, in the context of Andaman & Nicobar Islands, where water resource is by nature scanty, one should not pretend challenges will be easy but it is vital that a start is made now to avert the burgeoning crisis. The prime objective of the workshop was to discuss the major understandings in this direction. The selected technical papers compiled in this proceedings volume are conceived as showcase of what people are thinking toward resource management. I hope this compilation of works of accomplished scientists will enrich our understandings about water resources of Andaman & Nicobar Islands and help in proper conservation, planning and development of water resources in coming years.

(Dr. Indranil Roy) Central Ground Water Board, Eastern Region, Kolkata

CONTENTS Foreword Preface Selected Technical Papers Page No. 1.

Groundwater Hydrogeology of Andaman and Nicobar Islands

1-13

Indranil Roy, S. Chakraborty, A. Kar and G. C. Pati 2.

Delineation of Sea Water Intrusion Into Fresh Water Aquifer of South Andaman Island through Remote Sensing, Geophysical Techniques and Geographical Information System

14-21

Vazeem Iqbal, S. Balaji, Gulam Rasool Bhat and Balakrishna. 3.

Geophysical Studies in Hut Bay and Harminder Bay area in Little Andaman Island

22-27

Sujit Sarkar, S. K. Adhikari and Indranil Roy 4.

An Integrated Ground Penetrating Radar (GPR) and Geoelectric Methods for Deciphering Potential Ground Water Aquifers of Beodnabad Catchment, South Andaman Island

28-35

Shrikant Maury and S. Balaji 5.

Impact Assessment of Integrated Water Resource Management through Farmers Participatory Action Research Programme (FPARP) in Andaman and Nicobar Islands

36-41

A. Gayen, A. Zaman, A. Kar, S.K. Ambast and N. Ravisankar 6.

Rainwater Harvesting for Productivity Enhancement of Degraded Coastal Areas

42-46

A.Velmurugan, T.P.Swarnam, T.Subramani, S.Swain, M.S.Kundu, Nagesh Ram, Subhash Chand, Sankaran, M., and S. Dam Roy 7.

Fault Controlled Springs And Ground Water Potential In Ophiolite Rocks Along Brookshabad Fault - A Hydrogeological, Geomorphic And Structural Analysis

47-54

Gulam Rasool Bhat, S. Balaji, Showkat A. Bhat, Balakrishna and Mohsin H. Dar 8.

Quality of Surface water in Nicobar Islands, India

55-59

T. P. Swarnam, A.Velmurugan, Tulsi Pawan Sai, Priyanka Srivastava, Rachel and S. Dam Roy 9.

Delineation of Potential aquifer in Ophiolite formations of South Andaman Islands using Geophysical Techniques Balakrishna, S. Balaji, Shrikant Maury, Gulam Rasool Bhat, Vazeem Iqbal, Showkat Ahmad Bhat and Mohsin Hamid Dar

60-70

10.

Application of 2D Electrical Resistivity Imaging Technique to Assess the Ground water Potentials in the Port Blair Formation at Aberdeen Village near Joggers Park, South Andaman

71-81

S. H. K Murti, N. Ramanujam , P. Prasad, A. R. Quzi, K. B. Swapan, Chandrakant, A. J. Boopalan, A. Vignesh and Yuvaraj P. Mothilal 11.

Feasibility Study for Arresting Salinity Ingress in Tidal Channels in Parts of Middle Andaman and Baratang Islands, A & N Islands

82-89

S. Brahma 12.

Groundwater Quality Changes in Andaman and Nicobar Islands in Post - Tsunami: An Appraisal

90-95

Amlanjyoti Kar and K.K.Srivastava 13.

Ground Penetrating Radar and Resistivity Techniques in the Water Conservation Structures of South Andaman Islands – Issues And Challenges

96-106

S. Balaji, Shrikant Maury and Balakrishna 14.

Study on chemical quality of ground water in respect to domestic and irrigational need in Middle Andaman Islands K. K. Srivastava, A. Kar, A. Gayen and S. Upadhyay

107-115

TECHNICAL PAPERS

Proceedings of the Workshop on Conservation of Water Resources in Andaman & Nicobar Islands: Issues and Challenges; Organised by Central Ground Water Board at Port Blair, A & N Islands, March 27, 2014

Groundwater Hydrogeology of Andaman and Nicobar Islands Indranil Roy, S. Chakraborty, A. Kar and G. C. Pati Central Ground Water Board, Eastern Region, Kolkata Email: [email protected]

ABSTRACT Groundwater resource of Andaman and Nicobar Islands is gradually diminishing as a result of increased population and need of civilization. Though the island group receives on an average 3180 mm of rainfall, most of it goes away to sea due to rugged topography and deforestation. Erratic rainfall pattern coupled with population pressure in terms of increased ground water withdrawal and deforestation, making water resources of these islands unsustainable. It is observed that alluvium & colluvium of Holocene to Pleistocene period is the most potential water table aquifer. On the other hand, ophiolitic suite forms main deeper aquifer. Studies indicate gradual desaturation of these aquifer systems. To cope up with this situation, the only feasible solution is augmentation of the diminishing water resources with artificial recharge techniques. At this juncture, it is important to understand the groundwater potential of the islands as well as the formations of aquifers whose hold it. This paper attempts towards a summarisation of available information so that data gaps can be identified and a doctrine of proper management can be initiated. Key words: Hydrogeology, Aquifer potential

INTRODUCTION The Andaman and Nicobar Islands are situated as a dissected chain in arcuate fashion in the Bay of 0

0

0

Bengal off the Eastern Coast of India and extended between 6 and 14 North Latitude and 92 East Longitudes. These islands are forming two major groups, popularly known as Andaman group or the Northern group of islands and the other group of islands is called Nicobar or the Southern group of islands. With time these isolated group of islands once only occupied by ethnic tribes like Jarwas, Ongis, Sentinelese, Nicobarese became major occupancy of partition affected people after independence. Then onward there is significant growth in population and economics of the islands. With growth of population, there is significant impact on water resource (Fig. 1). Being a island scenario, exploitation of water resource is dominated by groundwater and rainfall. However, off late rainfall pattern is also changing. As the islands are mostly discrete and topography, types of vegetarian, forestry are varied, for being situated in a slender chain of nearly 740 km length, the rainfall distribution is highly varied and anomalous. This is quite evident from the rainfall record in the islands. Prior to 1990 the rainfall used to commence from first week of May every year while now it is receded to first week of June as happened in 2001, 2002 and 2003. In 2002 the situation worsened and Dhanikhari dam got dried-up and the Port Blair town water supply was totally shattered. Fortunately in 2004 the rainfall in Andaman District has been close to normal. These situations lead towards further dependence on groundwater. However this over dependence is leading towards overexploitation of the precious resource.

1


Growth of Population and Domestic Water Consumption 400000

18000 Population

16000

350000

14000

Population

300000

12000

250000

10000 200000 8000 150000

6000

100000

4000

50000

Domestic Water Consumption (m3)

Water requirement (m3)

2000

0 1900

1920

1940

1960

1980

2000

0 2020

Year

Fig. 1. Growth of population and water consumption

RAINFALL PATTERN The Andaman and Nicobar groups of Islands receive on an average 3180 mm of rainfall per annum with the highest rainfall experienced in 1961 (4300 mm) and the lowest in 1979 (1550 mm). Mean annual rainfall of Andaman District is and Nicobar Districts are 2629 and 2624 mm respectively. Islands are visited by South - West and North - East monsoons during the period from May to December. About 95% of annual rainfall is received during May - December (2250 mm in May – September during southwest monsoon and 685 mm in October - December during northeast monsoon) but due to erratic nature of rainfall the intermittent dry spells during the monsoon result in soil moisture stress. On the other hand annual evaporation loss is also very high and is about 15001800 mm. Nearly for a decade it is being observed that in most of the years the rainfall is below normal and in the lean period (i.e December to May ) the islands receive scanty rainfall. This had been creating the evacuation or drying up of the surface water in the reservoirs. As rainwater is the only source of the fresh water availability, its harvesting, storage and recycling forms the most important strategy for natural resource management in these islands.

GEOMORPHOLOGY AND DRAINAGE Andaman & Nicobar islands have varied topographical features. Main Andaman group of islands features a mountainous terrain with long ranges of hills and narrow valleys. Maximum altitude is at Saddle Peak, which is about 730 m amsl. On the other hand, topography of Nicobar Islands features undulating terrain with main ridges running North-South surrounded by long, sandy beaches. Katchal and Car Nicobar have almost flat plateau type terrain. In Great Nicobar and Little Nicobar, the land is very irregular, having steep hills and valleys. Mount Thullier in Great Nicobar is about 642 m amsl and is the highest in Nicobar group of islands. Deep inlets and creeks are formed by the submerged valleys. The coastal plain fringing the hilly terrain is 0.2 to 1.0 km wide with occasional coastal mounds, rocky shore line sandy beaches and mud flats. Geomorphologically the Andaman

2


and Nicobar islands can be divided into three broad units namely a) moderately to steep hill ranges; b) narrow Intermontane valleys; and c) limited gently sloping coastal tracts including swamps. Most of the islands are devoid of any big river systems and without major catchment. However, a few perennial streams such as Mithakhari, Protheropore nala, Burma nala, Pema nala, Karmatang, Betapur, Korang, Rangat, Dhamikhari, etc. drain the Andaman group of islands. The Great Nicobar is the only island of the Nicobar group with five perennial rivers. Coral reefs surround most of the Islands. This geomorphic situation restricts groundwater recharge. Surface run-off is high due to steep gradient. About 90% of surface run-off takes place during monsoon between May-November as revealed by discharge data. However, wide coverage by rain forest (86% of total area) holds water to some extent and is the main controlling factor of ground water recharge.

GEOLOGY The Islands are composed mainly of thick Eocene sediments deposited on Pre-Tertiary sandstone, silt stone and shale with intrusions of basic and ultra – basic igneous rocks. Basement is formed mainly by Ophiolitic suite. In terms of areal coverage, sedimentary group is most pervasive and occupy nearly 70% of the entire area of the islands while the igneous group covers nearly 15% while the rest 15% goes to the coralline and limestone formations. A simplified geological succession of Andaman & Nicobar group of Islands is given in Table 1. All these formation except the recent-sub recent group have undergone multiple phases of folding, faulting and upliftment documented in complicated structural patterns. Volcanic Islands of Narcondum and Barren belongs to the Sunda group of volcanoes, representing Sunda group.

Table 1. Simplified Geological Succession of A & N Islands Age

Group

Formation

Recent to subRecent

Quaternary - Holocene Group

Beach sands, Mangrove clay, Alluvium, Coral rags and Shell limestone, loosely consolidated pebble beds

~~~~~~~~~~~~

Unconformity

~~~~~~~~~~~~~~~~~~~~

Pleistocene to Late Pliocene

Nicobar Group

Shell limestone, Sandstone, Claystone, etc. Miocene Archipelago Group Upper white claystone. Melville Limestone

Pliocene To Miocene ~~~~~~~~~~~~ Oligocene to Paleocene

Archipelago Group Unconformity Andaman Flysh Group Mithakhari Group

~~~~~~~~~~~~~~~~~~~~ Thinly bedded alternations of Sandstones and siltstones, grit, conglomerate, Limestones, black shales, thinly bedded chert, pillow lava, etc.

~~~~~~~~~~~~

Unconformity

~~~~~~~~~~~~~~~~~~~~

Late Cretaceous

Ophiolite Suite

Dyke swarms, acidic suite, with Related ultramafic suite,etc.

3


HYDROGEOLOGICAL FRAMEWORK Hydrogeologically, there are several major aquifer system in the A & N islands, however their nature varies island to island and depends on underlying geological formation. The porous formation mainly consist of beach sand with coral rags and shells, along with the thin cover of alluvium in the valleys and foot hills adjacent to valleys, and the moderately thick pebbly valley fill deposits (colluvium) in the narrow intermontane valleys constitute water-table aquifer. The thickness of beach sand and alluvial deposits commonly ranges from 3 to 9 m. In Great Nicobar, this thickness is only 2 to 2.5 m. The colluvial deposits in narrow intermontane valleys e.g. Beadonabad valley has much higher potentiality. One bore well of 152 mm diameter was drilled by CGWB down to 3

16.50 mbgl tapping the total thickness of the saturated colluvial deposits and yielded 72 m /hr. Pumping this well for 500 minutes did not show any deterioration in chemical quality. The drawdown 2

was recorded as 5.67 m and Transmissivity was calculated to be 127 m /day. The well could cater to the domestic need of 10000 rural populations. The fissured formation represented by upper Cretaceous Ophiolite Suite of rocks includes basic volcanics, ultrabasic and intermediate to acid plutonic rocks. Based on the compactness and fracturing, as observed in exploratory drilling, these rocks are sub-classified as consolidated group and semi consolidated group. The fractured upper Cretaceous igneous rocks and the Lower Tertiary conglomerate, grits, graded sandstone (greywacke) and their weathered upper mantle form potential aquifer. The weathered mantle is generally 3 to 4 m thick but adjacent to the valleys it increase to about 6 m. The saturated thickness of the weathered mantle and the immediately underlying shallow fracture zones form the water table aquifer. Deeper fracture zones within 60 mbgl form semi-confined to confined aquifer. Fractured sedimentary rock covered areas were explored through 13 exploratory boreholes of which 02 boreholes were found successful i.e. Potheropore and Dilthaman Tank. At both the places Mithakari Sandstones and Shales were encountered, the productive fracture zones at Potheropore 3

between 25 to 60 m, but yielded 17m /hr water which is brackish. The borehole at Dilthaman Tank yielded very less but EC value was less and water was potable. The boreholes drilled at other places in the sedimentary rocks through dark grey shale of Mithakari Group were found dry. It is revealed from the study that the weathered sandstone are poor aquifers whereas the weathered volcanics rocks act as moderate to good aquifers at suitable locales. Results of 18 exploratory bore wells in South Andaman show that the deeper fractures imparting secondary porosity and permeability are restricted within 60 mbgl in sedimentary rocks and within 52.7 m in the volcanics and the intermediate plutonic rocks. The most productive fracture zones are in the volcanic rocks as noticed at Calicut in the depth range of 14-20 m, and 45-52 m where an intrusion of ultrabasic rock 3

(Serpentinites) was noticed. The yield of the bore well was recorded as 44.67 m /hr; drawdown after 2

500 minutes of pumping was 8.23 m and transmissivity of 139.6 m /day. The fractured volcanic rocks elsewhere are not productive e.g. Brichganj, Hamfreyganj as the yield of the tube wells were in the

4

Proceedings of the Workshop on Conservation of Water Resources in Andaman & Nicobar Islands: Issues and Challenges; Organised by Central Ground Water Board at Port Blair, A & N Islands, March 27, 2014 3

3

order of 1.18 m /hr and 0.52 m /hr respectively. It appears that the fractured volcanic rocks are most productive where they are intruded by the ultrabasics. The area covered with semi consolidated Lower Tertiary sedimentary rocks in the Great Nicobar Island were also explored and found the thin bedded fine grained sand stone – clay stone alternation may not be properly termed as aquifer. The maximum discharge obtained by tapping 31 m thick fine grained, soft argillaceous sand stone between 20 -92 mbgl was 187 lph and quality of water was found good. In sedimentary rock in valleys and adjacent to Bays, depth of dug wells are restricted to 3.5 to 4 mbgl, depth to water level in the dug wells in valleys 2.5 to 2.75 m, and in the igneous rock in same physiographic unit, depth to water level generally less than 3 mbgl, with a seasonal fluctuation around 1.5 to 2.5 m. Sp. capacity of lower Tertiary Sandstone, was found very low in the range of 1.12 to 261 lpm/m, in the weathered volcanic rock sp. capacity values was in the order of 0.79 and 9.55 lpm/m. In order to study the behaviour of ground water regime with time and space in Andaman group of islands 93 ground monitoring stations were established, and periodic water level measurements are being taken 2 times in the year, for pre-monsoon period during May and for the post-monsoon period during November/December. May, 2012 The Depth to water level generally varies, between 0-2m, 2-5m and 5-10m bgl. Majority of the wells show water level between 0-5m (97.8%). The minimum water level at 0.19 magl was recorded at Dhannikhari at South Andaman and maximum 7.40 mbgl at Calicut borewell of South Andaman. Depth to water levels mostly in the range of 0-2 mbgl (55.9%) followed by 2-5 mbgl (41.9%) and 5-10 mbgl (2.2%). November, 2012 The Depth to water level generally varies between 0-2m, 2-5m and 5-10m bgl. Out of 93 wells measured, water level in 87 wells varies in the range of 0-2 mbgl, in 04 wells in the range of 2-5 m bgl and in 02 wells in the range of 5-10 m bgl. The minimum water level was at 0.03 mbgl and recorded at Baratang of Middle Andaman and maximum water level i.e. 5.51 mbgl at Port Blair dugwell of South Andaman. Depth to water levels mostly in the range of 0-2 m bgl (93.5%) followed by 2-5 m bgl (4.3%) and 5-10 m bgl (2.2%). Hence, depth to water level in majority of the monitoring stations ranges between 2- 5 m (66%) and within 2 m (25%) in rest of the stations during May. The water level trend has been analysed for all measurements which shows that during 2002 – 2012 out of 65 analyzed well, 61 wells show rising trend of water level in the tune of 0.05 to 0.9 m/yr. Rest 04 wells show falling trend of water level in the tune of 0.09 to 0.46 m/yr. However during the same period the pre monsoon trend shows falling trend in most of the wells.

5


Fig. 2. Hydrogeological map of A & N Islands 6


Rural water supply in the entire A & N Islands except Neil and Car Nicobar Islands (water supply is done in these Islands only from the wells) is maintained either directly from the springs or spring or spring fed perennial streams. These springs are generally formed in high altitudes because of good fracturing in the rocks. However, the springs are highly yielding and sustainable in, igneous rocks and limestone as seen in Rutland (Kalapahar), Panchavati Hills (near Rangat) and Saddle peak (all in igneous rocks) and in Little Andaman and Havelock islands (limestone). GROUND WAER EXPLORATION During the exploration programme of CGWB in the period of 1984-90, 47 boreholes were drilled in the entire A& N Islands. Amongst these wells 18 were drilled in South Andaman, 11 were drilled in Middle Andaman, 02 in North Andaman, 09 in Great Nicobar, 03 in Nancowrie and 04 in Katchal Island. It was observed that the boreholes drilled in Sedimentary formations throughout did not yield except one near Prothrapore Jail Junction, which yielded brackish water (EC: 5500 µs/cm) to the tune of 9000 lph. However, the valley fill deposits in the islands were found to yield copiously. The well drilled by CGWB at Beadonabad is the main supply source in parts of South Andaman adjoining Beadonabad-Rangachang-Burmanala sector (44000 lph yield). Igneous rocks yield moderate to good. Down to 60 m depth potential fractures were noticed. The yield range were found to vary from 10,000 to 25,000 lph. There was no exploration in the coralline and limestone formation. Observations from these studies may be summarised as below: 1. Geology of the islands is highly varied and complex. Each Island is having separate geological characteristics; 2. Out of 47 exploratory wells only two were highly successful (one at Beadonabad and other at Calicut) and four other in Middle Andaman were partially successful; 3. Except in the areas underlain by the valley fill deposits and the pockets underlain by igneous rocks and Coralline formation, the prospect of ground water development is bleak; 4. Major parts of the islands are covered by unproductive sedimentary rocks; 5. Even in the terrains underlain by sedimentary rocks, a good thickness of porous valley fill deposits could be seen in many areas which carry a huge quantity of base flow throughout the year; 6. Lot of fresh ground water is flowing below the streams as base flow, besides the surplus runoff water move to the sea along the streams.

GROUND WATER QUALITY The quality of ground water throughout the island is neutral to alkaline as envisaged from the analytical results of water samples collected from the existing monitoring stations. As per analysis from samples collected during May, 2012, it is generally of the calcium bicarbonate type, and the bicarbonate content varies from 43 to 427 ppm greatly predominates over the chloride content varying between 7 and 390 ppm. Computation of the chloride-bicarbonate ratio of ground water from the islands varies between 0.1 and 0.2, which indicates that there is no large scale saline water intrusion. In general the ground water is fresh with low mineralization having Electrical Conductivity (EC)

7

Proceedings of the Workshop on Conservation of Water Resources in Andaman & Nicobar Islands: Issues and Challenges; Organised by Central Ground Water Board at Port Blair, A & N Islands, March 27, 2014 0

ranging from 200 to 750 µs /cm at 25 C, baring a few cases where well is located very close to sea, EC exceeds e.g. 1200 µs/cm e.g. at Corbyn’s cove, Marina Park (South Andaman), Mohanpur (North Andaman). Iron concentration in ground water is mostly within permissible limit.

Table 2. Summary of Aquifer Characteristics Group / Geological Period

Geological Formation

Aquifer Characteristics

Groundwater Development Potential

Alluvium & Colluvium

Occur in the narrow intermontane valleys and stream valleys overlying Flysch / Mithakhari Formations and Ophiolites. Highly porous. Thickness varies from 0.5m to 17m.

Base-flow occurs throughout the year. Subsurface dam / dyke highly feasible. Yield of tubewell may be as high as 128000 GPD. Dug well (5 - 6 m dia. and 6 m deep) with sub-surface dyke may yield 50 thousand to 2 lakh lpd

Mangrove swamp clay

Occurs in many places in South Andaman and in places near Rangat (Saberi and Dasarathpur villages).

Generally not suitable groundwater development.

Volcanics and Pyroclastics

- Needs further study Dug well with 5-6m dia and 2-4 m depth may yield 30-50,000 lpd with low capacity pump (1-1.5 hp). Such formations are less developed in Andaman Group of Islands.

Basalt, Andesite, Dacite and Pyroclastics (Barren And Narcondam Islands Volcanics)

Highly porous. However further study needed.

Springs are available and used for Police camp in Narcondam.

Jhirkarang and Outram Limestone, Outram Sandstone

Amongst various formations carbonate formations are highly porous and made of dead fossil shells of coral and other marine organisms. Solution cavities are formed in limestone and Chalk Formations.

Dugwells in Melville Formation having 5 – 6 m dia. and 6m depth may yield 1 to 1.5 lakh lpd. Springs are preponderant in such Formations and discharge copiously in Little Andaman and Havelock islands. Solution pores and channels in such formations can sustain plantation crops in the slopes.

Raised beaches

(Pliocene To Miocene)

form independent

Raised beaches are composed of lime-Sand, Coral rags and the silicic arenacious and argillacous sediments. Freshwater occur as thin lenses in the beach sediments and can be developed by shallow dugwells / scavenger wells / Skim wells with / without infiltration galleries.

Holocene To Pleistocene

Archipelago Group

Does not aquifer

for

Muralat Jig chalk and white clay stone Melville Limestone Round chalk and white clay stone

8


Group / Geological Period

Geological Formation

Aquifer Characteristics

Groundwater Development Potential

Strait Formation Andaman Flysch Group (Oligocene To Upper Eocene)

Mithakhari Group (Middle Eocene To Palaeocene)

Alternate Sandstonesiltstone-shale and conglomerate

These formations contain fine grained sandstone and shale intercalations which sometimes generate an impervious residue in the weathering profile.

Springs are common but yields dwindle with recession of monsoon. In Tugapur Limestone however, sustainable springs exist. Dugwells having 5-6m dia and 2-4m depth may have discharge of 4000-5000 lpd. Exploratory Borewells down to the depth of 121m remained unproductive. Shallow overlying alluvium in the stream valleys are the sole solution of sustainable water supply in the areas underlain by such formations.

Springs are preponderant and of sustainable yield. In North and Middle Andaman rural water supply is made from these formations. Depth of weathering varies from 3.5 m to 14m. Potential fractures exist within the depth range of 50-80m. Auto-flow condition exists at many places namely Calicut, New Bimblitan, Mecca Pahar etc.

Dugwells having 5-6m dia and 5-6 m depth may yield 30000-50000 lpd. Borewells of depth range 30 to 80 m are productive and may yield 50,000 to 80,000 GPD. Dug cum borewells are also feasible. In an integrated plan a dug-cum-borewell with subsurface dyke at Burma Nala (near Sagun Bagicha) has been estimated to yield 10,00000 lpd. In Kamota, Nancowrie, Bampooka and Tillonchang islands rural water supply is made entirely from these formations. At present these formations are commonly used as building materials. Unplanned quarrying of aquifer material are jeopardising the water balance.

Sandstone-gritconglomerate Tugapur Limestone Lica Black Shale Pillow Lava sequences Acid Volcanic, andesite with Diorite, conglomerate

Ophiolite Suite (Cretaceous) Mafic, Ultramafics

Older Metamorphic Group (Precambrian)

Restricted occurrence and in the uninhabited parts of North-Middle Andaman.

Undifferentiated

- Needs further study -

GROUNDWATER RESOURCE POSITION As per the GEC, 97 norm groundwater resources have been estimated for 36 inhabited islands of A & N Islands. Since water level data of all the Islands (i.e. all 36 Islands) are not available, the rainfall infiltration method is adopted. The deduced figures are presented in the Table 3. During calculation, the intermontane valley and relatively flat topographical areas are considered as recharge 2

areas. The hilly areas (5989.11 km ) having slope more than 20% are deducted from the geographical area available in the inhabited islands. The rechargeable area in the inhabited island is 1871.40 km 2

2

out of total geographical area of 7860.51 km . Rainfall infiltration factor utilized varies from 0.14 to

9


0.07 depending upon geology. If the present resource position is compared with earlier resource position, diminishing scenario becomes prominent, particularly in drinking water scenario. The comparison is given in Table 4.

Table 3. Groundwater Resource Position (as on 31st March, 2011)

Sl. No.

Assessment Unit (Island - wise)

Net Annual Ground Water Availability (ham)

Existing Gross Ground Water Draft for irrigation (ham)

Existing Gross Ground Water Draft for domestic and industrial water supply (ham)

Provision for domestic, and industrial requirement supply to 2025 (ham)

Net Ground Water Availability for future irrigation development (ham)

Stage of Ground Water Development (%)

2620.04

2.19

152.02

151.87

2465.98

5.89

1

North Andaman

2

Stewart Island

5.12

0.00

0.01

0.01

5.11

0.11

3

Aves Island

1.69

0.00

0.01

0.01

1.68

0.32

4

Interview Island

145.44

1.11

0.06

0.06

144.27

0.80

5

Middle Andaman

2040.02

5.26

104.24

104.13

1930.63

5.37

6

North Passage Island

10.92

0.00

0.04

0.04

10.88

0.38

7

Long Island

159.77

1.05

7.93

7.92

150.80

5.62

8

Bartang Island

162.95

2.14

21.86

21.83

138.98

14.73

9

Strait Island

8.77

0.00

0.15

0.15

8.62

1.72

10

Narcondam Island

7.02

0.00

0.06

0.06

6.96

0.86

11

East Island

15.79

0.00

0.06

0.06

15.73

0.38

12

Smith Island

92.55

0.00

2.44

2.44

90.11

2.64

13

Havelock Island

1112.99

9.27

22.27

26.80

1076.92

2.83

14

John Lawrence Island

40.44

0.00

0.11

0.13

40.31

0.26

15

Neil Island

1012.44

5.58

11.93

14.36

992.50

1.73

16

South Andaman

3839.77

20.62

756.89

910.82

2908.33

20.25

17

Rutland Island

5097.44

0.00

2.86

3.45

5093.99

0.06

18

North Sentinel Island

70.49

0.00

0.16

0.19

70.30

0.23

19

Little Andaman

2099.55

15.80

72.92

87.75

1996.00

4.23

20

Flatbay Island

24.62

0.00

0.04

0.05

24.57

0.18

21

Viper Island

0.60

0.00

0.01

0.02

0.58

2.45

22

Car Nicobar Island

6175.92

0.00

25.91

21.55

6154.37

0.42

23

Chowra Island

ANR

0.00

1.81

1.50

N.A

N.A

24

Teressa Island

191.44

0.00

2.59

2.15

189.29

1.35

25

Bampooka Island

39.92

0.00

0.07

0.06

39.86

0.18

26

Katchal Island

888.55

0.00

6.78

5.64

882.91

0.76

27

Kamorta Island

601.55

0.00

4.36

3.62

597.93

0.72

28

Nancowrie Island

230.32

0.00

1.18

0.99

229.33

0.51

29

Trinket Island

140.11

0.00

0.55

0.46

139.65

0.39

30

Little Nicobar Island

59.21

0.00

0.45

0.38

58.83

0.76

31

Kondul Island

301.12

0.00

0.19

0.16

300.96

0.06

10


Sl. No.

Assessment Unit (Island - wise)

Net Annual Ground Water Availability (ham)

Existing Gross Ground Water Draft for irrigation (ham)

Existing Gross Ground Water Draft for domestic and industrial water supply (ham)

Provision for domestic, and industrial requirement supply to 2025 (ham)

Net Ground Water Availability for future irrigation development (ham)

Stage of Ground Water Development (%)

79.11

0.00

0.19

0.15

78.96

0.24

1290.59

0.00

9.66

8.03

1282.56

0.75

32

Pilomilo Island

33

Great Nicobar Island

34

Peel Island

18.77

0.00

0.01

0.01

18.76

0.07

35

Porlob Island

14.14

0.00

0.04

0.04

14.10

0.31

36

Tillang-chang Island

48.42

0.00

0.02

0.01

48.41

0.03

Total (in ham)

28647.59

63.02

1209.86

1376.89

27209.18

4.44

Total (in bcm)

0.286

0.001

0.012

0.014

0.27209

4.44

Table 4. Comparison of the Estimate 2004 vs. 2010-11 Resource

Resource

Assessment

Assessment

2004 (ham)

2010-11 (ham)

Total annual ground water recharge

32673.00

30803.86

Net annual ground water availability

32598.50

28647.59

Annual Gross Ground Water Draft for irrigation (ham)

61.00

63.02

Annual Gross Ground Water Draft for drinking purpose

1197.36

1209.86

Annual allocation of ground water for domestic and industrial water supply up to 2025

790.67

1376.89

Available ground water for future irrigation use

31771.45

27209.18

Stage of Ground Water development

3.72%

4.44%

Safe

Safe

Comparative Criteria

Categorization for water development

future

ground

AUGMENTATION OF GROUNDWATER RESOURCE With increasing population pressure the water resource is getting scarce day by day. More over increased food production is also stressing the very resource. Irrigation water requirements in few islands like Neil, Havelock and Little Andaman is met from groundwater. Utilisation of groundwater from borewells became popular in parts of South Andaman which are underlain by hard rocks. This situation created stress on the limited resource of the hard rock aquifer. Moreover, studies

11

Proceedings of the Workshop on Conservation of Water Resources in Andaman & Nicobar Islands: Issues and Challenges; Organised by Central Ground Water Board at Port Blair, A & N Islands, March 27, 2014 th

indicate that 26 Dec 2004 earth quake and following tsunami event developed multiple water loosing fractures in deeper aquifers. This has caused drying up of many borewells and cessation of autoflowing condition as also lowering of water level. To tackle this situation, groundwater resource needs to be artificially recharged. As discussed earlier, the islands receive copious rainfall. Depending upon the hydrogeological situation as well as terrain condition the following structures may be considered for augmentation of groundwater resource with surplus runoff. The various types of structures are a) Ponds; b) Check dams; c) Sub surface dykes; d) Recharge shaft; e) Intake wells; f) Collector wells with infiltration gallery; g) Lift irrigation points; and h) Roof top rain water harvesting structures. A model design of artificial recharge and conservation of ground water is given in Fig. 3. In A & N Island generally big boulders, gravels and porous pebbles are laid in the stream courses as gabion structure. However, the base flow could be arrested by means of sub-surface dykes which may recharge the subsurface reservoir even in lean period. The recharged and conserved water may be utilized by means of dug well and dug-cum-bore well. Site specific combination of various methodology will ensure optimum result. However methodology should be adopted in the islands keeping in view of the fragile geo-environmental condition of the Islands. These methodologies are not new to A & N Islands. Rainwater harvesting in the island was done for the first time during 1998-2000 by the A & N administration tapping the roof tops. Rainwater harvesting through ponds were initiated long back by the Agriculture Department for development of irrigation and fisheries. A & N Administration had constructed about 200 check dams in the islands. However, the activities should be highly accentuated.

Fig. 3. Model design of Artificial recharge and conservation of ground water

CONCLUSION A & N group of islands have complex and varied hydrogeological set up. This variation is within an island as well as across the islands. Erratic rainfall pattern coupled with rugged topography and deforestation, making water resources of these islands unsustainable. Underlying aquifer systems also show wide variation in their water holding and yielding capacity. To cope up with this situation,

12


the only feasible solution is augmentation of the diminishing water resources with artificial recharge technique.

Acknowledgement: The authors express their sincere gratitude to Shri Sushil Gupta, Chairman, Central Ground Water Board, for his kind permission to publish the paper. Authors are also indebted to Dr. R. C. Jain, Member (SAM).

Bibliography Adyalkar, P.G and Najeeb, K.MD (1981) Report on Systematic hydrogeological investigation in parts of South Andaman and Neil Island in Andaman District, A & N Islands (Unpub. Report of CGWB). Banerjee, I (1988) Hydrogeology and Ground water Resources evaluation in parts of South Andaman and Campbell Bay, Great Nicobar Islands (Unpub. Report of CGWB) Bhattachrya, S (1997) Report on Hydrogeological investigation for of sites for ground water structure in the civil airport area Port blair, South Andaman (Unpub. Report of CGWB) Central Ground Water Board (2000) Experimental Artificial Recharge studies in Gauribidanur and Mulbagal Taluks Kolar Districts, Karnataka (Unpub. Report of CGWB) Chakraborty, T. L. (1990) Systematic Hydrogeological surveys in Parts of Middle and South Andaman (Unpub. Report of CGWB) Kar, A (2001) Hydrogeology of Andaman and Nicobar Islands (Unpub. Report of CGWB) Kar, A; Sarkar, S and Srivastava K.K (2002a) Water supply to rural and urban areas of Andaman and Nicobar Islands with special reference to application of article recharge and conservation technique. Nat. Seminar of Ind. Desalination association, Kolkata. Abs. Vol. Kar, A (2002b) Artificial recharge of ground water for augmentation of water supply and landscape development in Port blair town and A & N Islands. Nat. Seminar, LAWMI, Kolkata, Abs. Vol. Kar, A (2002c) Preliminary report on investigation of springs at Rutland Island as a possible water supply source to Portblair town (Unpub. Report of CGWB). Kar, A (2003) Augmentation of water supply situation through development of (Preexisting and new) dugwell and pond sources in Port Municipal area (Unpub. Report of CGWB) Lahiri, T. C. and Sen,M.K(1988) Environment of the Oceanic pelasediments associated with the Ophiolite assemblage, South Andaman Islands. Indian Minerals, 42, No.1 Vohra, C. P., Halder, D and Ghosh Roy, A. K (1989) The Andaman-Nicobar Ophiolite complex and associated Mineral resources-current appraisal. Phanerozoic Ophiolites in India. N.C.Ghose (ED), Sumna Publishers, Patna, pp. 281-315 (1989)

13


Delineation of Sea water Intrusion into Fresh Water Aquifer of South Andaman Island through Remote Sensing, Geophysical Techniques and Geographical Information System Vazeem Iqbal, S. Balaji, Gulam Rasool Bhat and Balakrishna Department of Disaster Management Pondicherry University Port Blair

ABSTRACT Coastal zone occupy less than 15% of the earth. The coastal habitats such as coral reefs, mangroves, and sea grass beds maintain a fragile balance in the coastal ecosystem. The importance of the coastal ecosystem is to be understood in its inter-dependence and inter-relatedness to various other ecosystem. Fresh ground water quality and availability in coastal areas is affected by seawater intrusion into coastal aquifers. Coastal water quality and ecosystem may be significantly affected by ground water pollutants that are transported into coastal waters by submarine ground water discharge. In South Andaman, half of the population live in the coastal areas and so, the areas affected by sea water intrusion is focused in the present study. The quality of the water in some parts of the South Andaman Island was affected due to 2004 Great Sumatra-Andaman Earthquake and the resultant tsunami which resulted in seawater intrusions in the dug wells, borewells and ponds of the coastal area. The sea water intruded areas were demarcated using the satellite imagery which gives an idea of the spatial distribution of the affected areas and the probability of future trends. IRS 1D 1998 and IRS P6 2010 Satellite imagery were interpreted to identify the sea water inundated areas. The chemical analysis of water samples show high TDS and Chloride values at several places viz Mithakhari, North Wandoor 1, North Wandoor 2, Ograbraj 1 and Ograbraj 2 which substantiates the sea water intrusion. TerraTEM electromagnetic survey was carried out at Mithakhari and Ograbraij to delineate the very high conductivity zone which may be a saline pocket. The Geophysical survey and chemical analysis of water samples have been integrated to understand the effect of seawater intrusion into the inland. The Arc GIS has been used to digitize the various thematic maps for layer analysis and it could able to depict the regions affected by sea water intrusion The integrated analysis of Remote Sensing, Geophysical survey and Chemical analysis of water samples could able to demarcate the areas affected by sea water intrusion and several suggestions were made for the sustainable development of ground water resource of South Andaman Islands. Key words: Seawater Intrusion, Geographical Information System (GIS), Remote Sensing, Geophysical Survey, South Andaman Island.

INTRODUCTION The Andaman and Nicobar Group of Islands are situated as a dissected chain in arcuate fashion oriented in N – S in the Bay of Bengal off the Eastern Coast of India and extended between 6 14

and

North Latitudes and 92 and 94º East Longitudes, covering a geographical area of 8249 sq. km.

These islands are forming two major groups, popularly known as Andaman Group or the Northern Group of Islands and Nicobar Group or the Southern Group of Islands. The capital town of all the groups which form the Union Territory is Port Blair.

Occurring to the east of the Indian mainland is an archipelago of over 500 islands, islets and rocks, known as the Andaman and Nicobar islands. These lie in the Bay of Bengal over 1200 kms east of the mainland referred to as the Bay Islands. These islands form an accurate chain and convex towards

14


West having an approximate North-South trend over a length of 780 kms. Within the geographical coordinates of 6 N to 14 N latitude and 92˚E to 94˚ E longitude. These islands are the emergent peaks of submerged mountains extending from the Arakan Yoma ranges of Burma in the North to Java and Sumatra in the Southeast. The Union Territory of Andaman and Nicobar was divided into three districts, namely, the North and Middle Andaman district, South Andaman district and the 0

Nicobar district. The Andaman group of islands occur North of 10 channel and has an area of 6408 sq kms which includes 24 islands having human settlement. Five of the largest islands, of this group, Baratang, Rutland, and North, Middle, and South Andaman, lie close together and are known as the Great Andaman. Another main island, Little Andaman, is separated from the cluster by the waters of 0

Duncan Passage. The Nicobar group of islands lie South of 10 channel, covering an area of 1841 sq kms with 12 islands having human settlement. The two districts are separated by 160 km sea. Baring a few islands in the Nicobar district, the terrain is mostly undulating with the main ridges running North-South. In between the main ridges, deep inlets and creeks are formed by submerged valleys. The islands have a large area under forest cover. The area under forest cover is 7171sq kms. which accounts for nearly 87% of the total area of Andaman and Nicobar islands.

CLIMATE The Andaman and Nicobar Islands receive rainfall from both the Southwest and Northeast monsoons and the maximum precipitation is between May and December. The islands enjoy tropical humid climate. The relative humidity varies from 79% to 89%, wind speed varies from 7 km/hr. to 10 km/hr. 0

0

0

0

while the maximum and minimum temperature fluctuate between 27 to 33 C and 21 to 25 C. Daily evaporation rate in the island is fairly high which cumulatively ranges from 1500-1800 mm per annum. The normal rainfall of Port Blair is 3180 mm whereas the mean annual rainfall of Andaman and Nicobar Districts are 2629.0 and 2624.0 mm respectively.

GEOMORPHOLOGY The Andaman group of islands generally features a mountainous terrain with long ranges of hills and narrow valleys. The maximum altitude of these islands is at Saddle Peak, which is about 730 m above mean sea level. The peak is formed of sandstone, limestone and clay. The slopes are also moderate. Hogbacks, sloping escarpment and cuesta landforms exist in sedimentary formations. There are also spurs running East –West in between the main ridges. Deep inlets and creeks are formed by the submerged valleys. Coral reefs surround most of the Islands.

MATERIALS AND METHODS The flow chart explain the systematic approach of the methodology. The change detection of sea water intrusions was done using IRS 1D 1998, IRS 1D and IRS P6 2010 satellite imagery (Anbazhagan, 2005 and Ashok Kumar, 2005).The digitisation and the layer analysis have been carried out using ArcGIS 9.1 software. The present study is focused to develop a sea water intrusion management plan for South Andaman Island and for this, sea water intrusion prone area were analysed. IRS 1D1998, IRS P6 2010 satellite imagery were used for estimating the sea water

15


intrusion. Ground water samples were collected from different places and were analysed chemically. On account of the large amount of ground water data collected for the South Andaman Island, a geodatabase was created by assigning an alphanumerical database together with a geographic database (Gou waixing, and Lawgiving 2002) so as to enable integrated methods to be adopted for studying the sea water intrusion in the coastal aquifer system (ESRI, 1969). The alphanumeric database created in Microsoft Access is associated with other parameters such as file name, location, chemical property, station name, depth of the well and height of the well etc.

The information

gathered in the monitoring network over the years of measuring campaign were organized into file containing well coordinates, elevations, water levels and month wise measurement of chemical analyses results, reference water samples and flow tests. Each shape file is composed of fields containing all the relevant information gathered for each well and records pertaining to the wells in the network. Query can be made in the input box. (Krishnamurthy, et al 1996) Feed the query and all information pertaining to that well will be displayed and modification can be made for monthwise or yearwise. Similar operations can be performed for other wells in the input box. To enable new input, modifications can be made thereof and all the information will be displayed which is the database “mask” was created with “coordinate and elevations”, “water level” and “chemical analysis” of each month of measurement. For example Jan 2013 and March 2013 etc. And the query is linked together by actions key. In each mask, it possible to know:

•

Information concerning a specific well, pond or bore well.

•

Access to other marks

•

Print the reports of the data after preview

•

Return to the last marks display.

The geographical database, ArcInfo and ArcView software organize the information into “views” and “theme”. A view is an interactive map that allows one to display, explore, query and analysis geographical information. It is made up of layer of geographical information. Each layer is called a “theme” which is a collection of different parameters that includes chemicals, locations etc. The SQL connection feature can access and query the Access database to retrieve record therefrom.

TerraTEM electromagnetic survey has been done in some selected places of South Andaman by in loop method. In this survey, the TX area =625 (m2) and Rx = 49 (m2) was covered. Profiling was done from one station to another station using in loop method.

STUDY AREA The study area namely South Andaman Island is the Southernmost Island amongst the Andaman o

o

o

o

Island which is located between 11 14’584” N and 11 28’748” N and 92 310’10” E and 94 46’583” E which includes Great Andaman (Fig.2). The Port Blair, the capital of the Andaman and Nicobar Island is located in the South Andaman and is the third largest in the Island group. The South Andaman 2

Island is 93 Km long and 31 Km in width which spans to an area of 1348km . It had a population of 2,

16


37,586 as per the 2011 census. The South Andaman is less mountainous than the North Andaman Island. The South Andaman Island comprise of sedimentary rocks of Andaman Flysch and Mithakari formations and Ophiolite Igneous suite of rocks. The sedimentary rocks include Sandstone, Shale and Siltstone and the Ophiolite suite consists mainly of Basalt, Andesite, Gabbro, Ultramafics and Tectonites.

RESULTS AND DISCUSSION Saltwater intrusion occurs naturally in most coastal aquifers, owing to reverse hydraulic gradient (Bruington 1969). The saltwater contains higher mineral content than freshwater and hence is denser. It has higher water pressure, as a result, seawater can propagate inland beneath the freshwater which is less dense and floats on the seawater (Bruington, and Sears, 1965,). As a result of pressure and density differences, saltwater move into coastal aquifers in a wedge shape under the freshwater, at the lowest point of the aquifer. The saltwater and freshwater meet in a so called transitions zone where mixing occurs through dispersion and diffusion. Certain human activities have increased the seawater intrusion in many coastal areas importantly ground water (Ackerman at al 1971) pumping from fresh water wells near the coasts. Water extractions drop the level of fresh ground water reducing its water pressure and allowing seawater to flow further inland. Other responsible influences include navigations channels, agricultural and drainage canals which provide conduits for seawater flow and sea level rise (Anderson, 1976). Seawater intrusion can also be worsened by extreme event like hurricane and storm surges. When fresh water is withdrawn at a faster rate, then it cannot be replenished, the water table fall down and drawdown results. This drawdown also reduces the hydrostatic pressure. When this happens near a coastal area, seawater from the ocean is pulled into the fresh water aquifer. The result is that the aquifer becomes contaminated with seawater (Bhattacharya, 1990 and Back, 1966).

Some parts of South Andaman Island were affected from seawater intrusion mainly because of the 2004 tsunami. The seawater affected places are Mithakhari, North Wandoor 1, North Wandoor 2, Ograbraj 1 and Ograbraj 2 and ground water sampling have been done and analysed for these locations. The area intruded by Sea water and the Ground water sample location is shown in Fig.3. and the chemical analysis of the ground water samples of these places has shown a higher TDS more than the permissible limit of drinking standard as per Bureau of Indian Standard 2001 (Tables 1 and 2.

Electromagnetic survey using TerraTEM was carried out at Mithakhari and Ograbraij by adopting the inloop method to bring out the high conductivity zone which is likely to be a saline pocket. The Terra TEM image clearly delineate the very high conductivity zone at Mithakhari and Ograbraj substantiated by the high conductivity values (Table 3, Figs. 4 and 5).

17


Fig. 1 Flow chart showing the Methodology

Sea water intruded area and Ground water sample location

Fig. 2 Study area - South Andaman Island

Fig. 3 Seawater intruded areas – South Andaman

18


Table 1. Chemical analysis of ground water for the month of January 2012 Constituents ( Parts Per-Million) Sample No

Locations

pH M/L

TDS M/L

Hardness value M/L

Chloride value M/L

Alkalinity value M/L

Iron value M/L

Fluoride M/L

1

North Wandoor 1

6.5

912

290

320

150

1

0

2

North Wandoor 2

7.2

2556

670

1410

50

0

1

3

Wandoor

6.5

1104

300

340

200

0

1

5

Ograbraij 1

7

912

210

300

250

0

1.5

6

Ograbraij 2

7.5

4596

1260

3830

30

1

0.5

7

Mithakhari

7.5

4466

1360

3430

255

1

0.6

Table 2. Chemical analysis of ground water for the month of March 2012 Constituents ( Parts Per-Million) Sample No

Locations

pH

TDS

Hardness

Chloride

Alkalinity

Fluoride

M/L

Iron value M/L

M/L

M/L

M/L

M/L

M/L

1

North Wandoor 1

8

16,860

7000

7000

80

0.3

0

2

North Wandoor 2

7

4164

50

3470

170

0

0

3

Wandoor

7.5

1092

250

310

350

10

5

5

Ograbraij 1

7

10524

3800

4600

370

0

1.5

6

Ograbraij 2

7

14100

3340

10520

240

0

1

7

Mithakhari

7.5

15100

3345

10530

360

0

1

Table .3 TerraTEM Electromagnetic profile results STATIONS NO

LOCATIONS

CONDUCTIVITY (MS/M)

LAYER THICKNESS (M)

1.

Mithakhari

1478

20

2.

Ograbraj

4701

40

19


Sea water intrusion

Fig 4. TerraTEM survey profile at Mithakhari

Sea water intrusion

Fig 5. TerraTEM survey profile at Ograbraij

20


CONCLUSION The satellite imagery clearly demarcated the sea water inundated area at Mithakhari, Ograbraij and North Wandoor. The interpretation of TerraTEM images clearly brought out high conductivity or saline pockets at Mithakhari and Ograbraij. The ground water samples collected at North Wandoor 1, North Wandoor 2, Wandoor, Ograbraij 1, and Ograbraij 2. Show a very high TDS and Chloride value which more than the drinking water standard is as are prescribed by BIS 2001. The integrated Analysis of Remote Sensing, Geophysical and Chemical analysis of ground water have substantiated the area affected by sea water intrusion.

REFERENCES Anbazhagan, S, (2005).Geospatial technology inground water Resources explorations andmapping Geospatial Technology for the Development planning, Allied publisher Chennai. pp: 215-22. Ashok Kumar (2005). 3D numerical ground water modellingof weathered aquifer system – A case study in LapsiyaWatershed, Hazaribagh, India. Geospatial Technology for the development planning, Allied publisher Chennai.pp:183-202

Ackerman, N, L; and Y.Y Chang, 1971, “saltwater interface during ground water pumping, Journal Hydraulics Div., ASCE. Vol, 97, No HY2 pp 223-232. Anderson .H.R., 1976 Ground water in the San Juan metropolitan, area, Puerto Rico, US Geological surveyWater –resources invest. 41-75, pp 107. Bhattacharya, B B (1990). Hydrogeological and Groundwater resources of Hazaribagh district, Bihar, Unpublished Report of Central Ground water Board, Patna. Bruington, A.E., 1969,”Control of seawaterintrusion in a ground water, Vol, 7, No3, pp 9-14.

Bruington, A.E, and F. Sears, 1965, “Operating sea water Barrier project. Jour. Irrig. Drain. Div ASCE, Vol .91, No1121, pp17-140. ESRI, (1969) .Arc info Training course class material Environmental system ResearchInstitute, Redland, CA, ESRI. Inc. Gou waixing and Lawgiving. C.D (2002), User’s guide to SEAWAT. A computer program for simulations of three-Dimensional Variable – density Ground water flow: Technique of waterResources investigations Book 6, chapter A7, pp 77 Krishnamurthy, J Venkatesh Kumar, Jayaraman, V.and M .Manival. (1996) an approach to demarcate Groundwater Potential zone through remote sensing and Geographical information system. International Journal of Remote sensing.17 (pp.1867-1884).

21


Geophysical Studies in Hut Bay and Harminder Bay area in Little Andaman Island Sujit Sarkar, Indranil Roy and S. K. Adhikari Central Ground Water Board, Eastern Region, Kolkata Email: [email protected]

Abstract Geophysical resistivity study has been carried out to assess the impacts of earth quake and tsunami th (26 Dec 2004) on water resources of Little Andaman Island. The main aims were to check the potability condition (chemical) of existing water sources in the Island both in the affected and unaffected areas and to find locales for ground water abstraction. 24 nos VES has been carried out in and around Hut bay. Prepared geo-electric sections shows that the ground water is almost significantly contaminated in Hut bay – Harminder Bay area by tsunami induced saline water. Keywords: Geophysical resistivity study, Geo-electric sections, VES, Water resource

INTRODUCTION Little Andaman is the southernmost island in Andaman district and it is bounded within the latitude 92°22’40” N to 92°36’16” N and longitude10°30’24” E to 10°54’00” E. Little Andaman forms a Tahasil and its HQ is at Hutbay. Extensive geophysical resistivity study has been carried out to assess the th

impacts of earth quake and tsunami (26 Dec 2004) on water resources of the Island. The main aims were to check the potability condition (chemical) of existing water sources in the Island both in the affected and unaffected areas. To adjudge the quality of the well water in highly affected, partly affected and marginal areas for mitigation through flushing of wells by means of dewatering to decipher the disposition of saline and fresh water with a perspective to carryout ground water exploration (drilling) in the Islands to mitigate the water supply problem through construction of the bore wells as also by dug wells. And finally, to find out the necessity of fresh water conservation adopting rooftop rainwater harvesting and recharge, construction of check dam, subsurface dam, collector well, pond etc.

HYDROGEOLOGICAL FRAMEWORK In the area Recent to Sub-Recent coralline sands form potential aquifer in the shallow horizons. Depth to water level varies from 2 to 3 mbgl in post-monsoon and 2.5 to 4 mbgl in pre-monsoon periods. These aquifers are mostly developed by dug wells. The yield of a dug well (typically of 3 m dia and 5 m depth) vary from 1.0 Lakh to 2.0 Lakh litres per day. The areas where such type of formations crop out are mainly (i) Harminder Bay, (ii) Netaji Nagar, (iii) Hut Bay, (iv) Dugong Creek and (v) South Bay (Onge settlement) areas. Only in tribal settlement areas the water supply was being met from the dug wells through pumping. The Hut Bay settlement was provided water from a natural spring which forms a fall near Km No. 6. The pervasive and vast limestone terrain form potential reserve of Ground water. Good high yielding springs, waterfalls and highly flowing streams are developed in this formation.

22


Characteristically these limestones are highly cavernous Many high yielding springs with falls ranging in height from 12 to 18 m exist in these formations. From such springs major streams are developed which forms good water sources in the areas unfortunately such streams are not developed in Little Andaman except the dams constructed at R.K. Pur and Ravindra Nagar and huge fresh water is going unabatedly to the sea. One such high yielding springs (untapped) was studied which is called JhaoJhao source discharging >500 lps even during summer. Similarly there are springs at Krishna Nallah and the spring-cum-water falls (discharge more than 100 lps) at Km No.6 which is tapped for water supply in Hut Bay area through intake wells (with gallery) constructed at the stream course. Similarly in the Chandan Nallah (Km No. 16 Nallah at R.K. Pur) stream course one intake well with gallery is constructed. From this source entire water supply to the settlement area at R.K. Pur, V.K. Pur & Ravindra Nagar is met.

GEOPHYSICAL STUDIES A total of 75 numbers of Vertical Electrical Sounding (VES) were carried out at different parts of the Little Andaman island namely i) Hut Bay, ii) Harminder Bay , iii) Vivekanandapur, iv) Rabindra nagar, v) Ramkrishnapur, vi) Netaji nagar and viii) Dugang Creek areas. In Hut Bay and Harminder Bay area, a total of 24 VES were carried out to find out the fresh drinking water sources as well as to assess the feasibility of ground water exploration through drilling in the areas after the effect of tsunami & earth quake in connection with relief and rehabilitation work for victims. The electrical resistivity surveys were conducted by deploying an AC resistivity meter, ABEM Terrameter SAS300B, Sweeden.

RESULTS and INTERPRETATIONS During the survey maximum current electrode separation was kept as 400m (AB), Plotting the apparent resistivity values against half electrode separation in double log paper, VES curves were generated and these curves were interpreted with the help of standard master curves by partial curve machine technique. The curve types obtained in Little Andaman were K, A, Q, HA, KQ, KH, H type. All the interpreted results are tabulated in Table 1 and 2. These results are standardized with the known lithology of the nearby tube wells /dug wells and the resistivity values for different formations are furnished below in Table 1.

Table 1. Standardized resistivity ranges for different formations in Little Andaman SL. No.

Resistivity (Ohm-m)

Formation

1.

Top soil

4 – 1250

2.

Fresh water in cavernous limestone / coralline sand

30 - 480

3.

Brackish water in cavernous limestone / coralline sand

4.

Brackish to fresh water in cavernous limestone / coralline sand

20 - 29

5.

Highly weathered formation/ clay

12 - 14

6.

Saline formation water /clay

7.

Hard formation (dry)

8 - 18

0–7 560 - 3075

23


Table 2. Summary of VES Results in Hut-Bay – Harminder Bay Area

Sl. No.

Resistivity ( ohm-m)

VES No.

Location

Thickness (m) Depth H (m)

ρ1

ρ2

ρ3

ρ4

h1

h2

h3

h4

1.

Infront of APWD-Guest house, Hut-bay, NE-SW

SK-1

16

8

Very Low

1.6

1.12

2.7

2.

Beside workshop 50 m west of (SK-I)

MK-2

10

24

Very Low

1.9

0.2

2.1

3.

Senior Secondary 100m West of MK-2

SK-3

8

74

Very Low

1.8

1.26

3.06

4.

Senior Secondary School 100 m West of SK-3

MK-4

9

23

Very Low

3.2

1.6

4.8

5.

APWD pump house

SK-5

7.5

6

1.2

1.3

11.7

6.

200m south of SK-5

MK-6

80

200

10

1.3

1.3

7.

100m east of MK-6

SK-7

54

135

Very Low

1.3

6.5

8.

200m east of SK-7

MK-8

200

625

325

8

1.6

9.45

4.6

17.6

9.

250m east of MK-8

SK-9

2

1

2

VL

2

4.4

6

12.4

10.

100 m south of Road Junction ½ Km from sea shore.

MK-10

5

2

VL

1.5

3.3

11.

200m south of MK-10

SK-11

12

62

28

1.8

8.1

12.

150m south of SK-11

1.5

7.5

9

13.

3.1

9.3

12.4

School

∝

2

13 6.5

9.1 7.8

4.8 16.5

26.4

MK-12

12

30

Very Low

300m south of VHAI camp

SK-13

14

4

1

14.

100m east of SK-13

MK-14

20

30

4

1

2.2

3.08

13

18.3

15.

VHAI relief camp

SK-15

1000

1250

345

16

1.8

1.44

1.8

5.4

16.

In front of Mr.Irlappan’s residence, 250m south of VHAI camp

MK-16

14

49

11

2

1.55

3.1

19.2

23.85

17.

In front of Mr. Irlappam residence, (20m east)

Sk-17

14

49

18

1

5.3

6.2

20.0

31.4

18.

Behind MK-16 (100m east)

MK-18

47

168

18

2

4.3

2.2

15.3

21.8

19.

Near Rotary Club; Along road side

SK-19

5

9

3

1

2.7

4.6

23.5

30.81

20.

Beside the Temple; Along road side

MK-20

7

18

6

1

2

2.8

11.5

16.3

21.

Near House of Shakeel

SK-21

14

27

12

2

1.8

1.27

7.9

10.98

22.

50 m East Shakeel

MK-22

20

25

12

VL

2.2

1.54

13.3

17.0

23.

Adjacent to Open Well at Harminder Bay

SK-23

111

555

46

8

1.8

0.9

5.72

8.38

24.

100 m towards sea – ‘E’ of SK-23 at Harminder Bay.

MK-24

7

68

16

2

1.41

3.63

22.5

27.6

of

house

of

Different characteristics of the aquifers at various depths are analysed and summarised to generate sections along AB, CD, EF and GH on the basis of the resistivity results. General character of them are:

24


A. Geo-electric section along AB The section AB passes through the VES MK6, SK7, MK7 and SK9. It is observed that except VES SK23. It shows partly freshwater formation (in the western part) and partly saline formation (in the eastern part) as the resistivity values show 10 ohm-m and 8 ohm-m respectively (Fig. 1a). From this section it is clear that saline water, mixed with ground water at eastern part (close to sea and underlain by coralline sand) entered into the ground at western part (cavernous limestone). Fresh water and brackish water is floating over saline water in the western part.

B. Geo-electric section along CD This section passes through the VES SK13, MK14, SK15, MK16, MK18, MK12, SK19 and SK 21 and oriented in W – E direction (Fig. 1b). The range of top soil resistivity is 6 to 1000 Ohm-m. Below this top soil a fresh water bearing layer of 3.08 to 6.5m thick and 30 to 345 ohm-m resistive is available in partly cavernous limestone (in the western part) and in partly coralline sand (in the eastern part). At VES SK15 a dry massive formation of resistivity 1250 is identified over the brackish coralline limestone of resistivity range 11 ohm-m to 18 ohm-m. At VES SK 21 a thin layer (1.8m) of resistivity 27 ohm-m (Brackish to Fresh water) is floating over the brackish water layer of resistivity 12 ohm-m. below these layer the bottom layer is saline. In both the section it is observed that middle portion of the section is bulging, hence the aquifer is thick at these portions.

C.

Geo-electric section along EF

The section EF passes through the VES MK4, SK3, MK2, SK1 and SK23. It is observed that except VES SK23, located at Harminder bay, all the VES at northern part are showing a thin layer of fresh and brackish water (thickness 0.2m to 1.6m) are floating over saline water (Fig. 1c). The resistivity range of this thin layer is 8 ohm-m to 74 ohm-m. As these VES were close to the sea and the resistivity order is lower, the formation is predicted to be coralline sand. VES 23 is located at little distance from the sea shore and the fresh water pocket of resistivity 46 ohm-m is found to be sandwiched between upper dry limestone ( resistivity 555ohm-m) and lower brackish formation of resistivity 8 ohm-m, it is inferred that the fresh water is lying within limestone cavity.

D. Geo-electric section GH This section passes through VES MK10, SK11, MK12, SK21, MK22 and MK20 along N - S orientation. Range of resistivity reveals that the section lies in the coralline sand. Though the area is lying within the tsunami affected zone, the VES SK11 and MK12 show a good fresh water column and the VES SK21 and MK22 show brackish to fresh water column laying within the depth range 3-10 mbgl. All these layers are floating over brackish and brackish to fresh water aquifer. Presence of potable water may be due to withdrawal of water by the user and a probability of a connection of spring source with the aquifer (a nala flowing close to the VES SK11 ad MK12)

25


(A)

(B)

(C)

(D)

Fig. 1. Various Geo-electric sections in Hut bay Area

26


CONCLUSION From the study of geo electric sections it is clearly understood that the ground water is almost significantly contaminated in Hut bay – Harminder Bay area by tsunami induced saline water. VES point SK1, MK2, SK3 and MK4 are directly located in the devastated area. Only a very thin layer of fresh to slightly brackish water (0.2 to 1.6 m) is floating over saline water. VES, SK-7, MK14, SK15, MK16, MK18, SK11 and MK12 indicates a fresh water column lying within the depth range 1.8 to 8.1 mbgl and is floating over the brackish and saline water. Results show that ground water borewell may be constructed down to the depth 40 m at VES, SKI, MK3, MK11, SK4, MK10 MK9, MK8 etc.

Acknowledgement: The authors expresses his sincere gratitude to Shri G. C. Pati, Regional Director, Central Ground Water Board, Eastern Region, Kolkata for his guidance and kind permission to publish this paper.

REFERENCES Adyalkar, P.G and Najeeb, K.MD (1981) Report on Systematic hydrogeological investigation in parts of South Andaman and Neil Island in Andaman District, A & N Islands (Unpub. Report of CGWB). Banerjee, I (1988) Hydrogeology and Ground water Resources evaluation in parts of South Andaman and Campbell Bay, Great Nicobar Islands (Unpub. Report of CGWB). Chakraborty, T. L. (1990) Systematic Hydrogeological surveys in Parts of Middle and South Andaman (Unpub. Report of CGWB) Kar, A (2001) Hydrogeology of Andaman and Nicobar Islands (Unpub. Report of CGWB). Kar, A; Sarkar, S and Srivastava K.K (2002a) Water supply to rural and urban areas of Andaman and Nicobar Islands with special reference to application of article recharge and conservation technique. Nat. Seminar of Ind. Desalination association, Kolkata. Abs. Vol.

27


An Integrated Ground Penetrating Radar (GPR) and Geoelectric Methods for Deciphering Potential Ground Water Aquifers of Beodnabad Catchment, South Andaman Island Shrikant Maury* and S. Balaji Department of Disaster Management, Pondicherry University, Port Blair 744 103 *Email: [email protected]

Abstract As the population increases, the demand for Ground Water increases exponentially. Though, the Andaman and Nicobar Islands receives copies rainfall, it faces severe scarcity for Ground Water during lean season. In this context, an attempt has been made to tap the potential Ground Water aquifers in order to meet out the demand for Ground Water using integrated techniques involving GPR and Resistivity methods. A total of eight GPR profiles and nine VES using Schlumberger electrode configuration were carried out covering the entire study area and results were integrated with borehole lithologs. The combination of this data has provided a close correspondence on subsurface hydrogeological conditions. Based on the integrated results, the potential Ground Water aquifers were clearly demarcated. The integration has proved the efficacy of GPR and Resistivity techniques is quite useful in this art of investigation.

1 Introduction The major sources of water supply in Beodnabad, South Andaman Island are small streams, springs and dams while ground water is the only alternative source for water supply during peak summer. Since last decades, the ground water supply has increased due to its huge demand to support population and other commercial activities. So, exploitation, development and management of sustainable ground water potential is a dire need of the day. To assess the ground water potential, a joint venture of integrated technologies viz. geoelectrical resistivity and Ground Penetrating Radar (GPR) has been used to target water bearing fractures and porous formations. Further, in order to understand how ground water evolves in different hydrogeological settings of Ophiolite formations, an integrated geophysical survey involving VES and GPR has been carried out.

The integrated geophysical techniques embodying savvy prowess can be useful for a highly hydrologically complex geological terrene of Ophiolitic assemblage of Beodnabad watershed. A total of eight GPR profiles and nine VES using Schlumberger electrode configuration were carried out covering the entire study area. Further, to clearly understand the subsurface configuration, the geoelectric section and GPR image section results were integrated and matched with borehole lithologs. The combination of this data has provided a close correspondence on subsurface hydrogeological conditions. Geo-resistivities techniques globally accepted for their cost effective and versatility in the investigation of ground water potential and problematic zones for its sustainable exploration, development, and management avenues (Flathe 1955; Zohdy 1969; Koefoed 1979; McDowell 1979; Taylor 1982; Edet and Okereke 2002; Deceuster et al. 2006; Oyedele et al. 2009; Maury and Balaji 2014). The geo-resistivities survey viz. Electrical Resistivity Tomography (ERT) and Vertical Electrical Sounding (VES) are well established techniques, as a surface geoelectrical survey

28


tool (Taylor 1982; Loke and Barker 1996; Barker and Moore 1998). However, when geo-resistivity methods are used, limitation can be expected if ground inhomogeneities due to e.g. porosity, water content, lithology of subsurface layers, and anisotropy are present (McNeill 1980; Goldman and Neubauer 1994; Parasnis 1997; Park et al. 2007; Khalil 2010; Maury and Balaji 2014) and these are highly varies in the case of highly complex typical geological formations e.g. South Andaman Islands (Maury and Balaji 2014). These spatial scale ground heterogeneity in resistivity methods affect the resistivity values, so sometime, it is very difficult to interpret and identify the ground water occurrence accurately by using resistivity method alone. To optimize prediction and effective interpretation of resistivity data, borehole lithologs are much indispensable for the determination of change and characterization of subsurface properties investigation (Park et al. 2007; Khalil 2010; Maury and Balaji 2014). Hence, the site investigation based only on geo-resistivities alone has a significant risk due to these techniques owing to less resolution than electromagnetic/GPR while discriminating subsurface details and spatially evaluating and characterizing ground water potential in typically complex geological formations. The GPR technology has proved its efficacy to be a powerful geophysical tool on various subsurface and high resolution hydrogeological avenues for the ground water studies. GPR method widely used to interpret and model subsurface structures, hydrofacies and aquifer geometry (Cook 1975; Rubin and Fowler 1978; Ulriksen 1982; Olson and Doolittle 1985; Davis and Annan 1989; Beres and Haeni 1991; Doolittle et al. 2006; Bayer et al. 2011; Maury 2012). GPR is quite successful to detect contaminants in ground water aquifers (Daniels et al. 1990; Benson 1995). To obtain high resolution data interpretation from subsurface

number of investigators such as

Goldman and Neubauer (1994), Buselli and Kanglin (2001), Sandberg et al. (2002), Ezersky (2008), Parker et al. (2010), Pellicer and Gibson (2011) and Doetsch et al., (2012) have successfully carried out integrated study by electromagnetic/GPR and geo-resistivity techniques to understand complex hydrogeological aspects related to aquifers and bedrock fractures, while Greenbaum et al. (1993) and Deparis et al. (2008) successfully integrated remote sensing with resistivity techniques and electromagnetic/GPR to understand the complexity of fracture networks and their patterns related to ground water exploration.

2 Study Area 2

The Beodnabad catchment area is of 7.34 km and geographically ambit between

11°36’27’’ to

11°34' 30'' North latitudes and 92° 42’24’’ to 92°4 4’21’’ East longitudes (Fig. 1). The drainage pattern of the rivulet follows a sub-dendritic pattern. The major geological rock settings of this area are Ophiolitic complex, majority comprised of Tholiitic Basalt. The Ophiolitic complex of the study area is characterized by strong heterogeneity, repetitive deformations and multiple intrusions of steep to gentle slopes topography including coastal tract.

3 Materials and Methods The study was carried out in stages. These stages being: data collection, data analysis, data evaluation, data interpretation and reporting. In order to assess the ground water potential of the Beodnabad catchment, a complete geological, geophysical, and geotechnical study has been carried

29


out covering entire study area. Ground Penetrating Radar (GPR) and Vertical Electrical Sounding (VES) incorporated with borehole lithologs were used to determine structural and lithological characteristics of subsurface formations. With specific reason, the use of GPR techniques can quantify and describe subsurface information such as cavities, conduits and fractures, while resistivity technique can well explain subsurface geoelectrical properties are appropriate to strengthen and revolutionize the hydro-geological interpretations related to this research work (Maury 2012).

3.1 GPR Methods Appropriate GPR methods and antennas were adopted for subsurface investigation under the given condition. The resulting GPR profile images were further enhanced by various techniques such as filtering, deconvolution, migration, transform and other related analysis and corrections. For a successful GPR survey, a compromise between the required range (depth) and the ability to resolve one feature from another (resolution) has to be made. To optimize the GPR performance up to more depth, center frequency antennas of different frequencies were used to unravel the subsurface details like fractures, folds, faults and other lithological units (Fig.2).

3.2 Resistivity Methods A VES survey using the linear four-electrode Schlumberger electrode configuration was carried out at 9 locations falls on GPR profile (Fig.1) of the study area to ascertain the conductivity and/or the resistivity of the subsurface formations. The current electrode (AB) separations varied from 80-120 meter for the current electrodes (AB) and from 0.5 m to 3 m for potential electrodes (MN). The apparent resistivities obtained from the field measurement were plotted against half current electrode (AB/2) separation of apparent resistivity on a log-log graph. The VES curves were interpreted qualitatively and quantitatively by using a partial curve-matching technique and interpreted by IPI2win computer software to produce resistivity model with resistivity and the thickness of different layers of least RMS-error between the field and calculated resistivity values. The interpreted VES data has provided information in terms of four geoelectric layers with thickness (Table 1).

Further, two

traverses at an average profile spacing ~ 600 meter were made along different directions (Fig. 3).

4 Results and Analyses The GPR and VES resistivity models were validated for subsurface structural and hydrogeological properties to avoid non-predictive bias interpretation by correlating the GPR and VES results with the known lithology from borehole lithologs. A total of four borehole lithologs were obtained by using rotary as well as DTH drilling rigs for the correlation with interpreted GPR and VES data. The correlated results of GPR and resistivity with borehole lithologs were useful to fix the resistivity ranges and structural discrimination of various lithological units and to prepare conceptual structural and lithogeoelectric sections (Fig.4). Based on the subsurface information, the structural and litho-geoelectric section renders an approximate pictorial form of the subsurface structural conditions and resistivity distribution, which can be much helpful in the quantitative interpretation of ground water potential. A litho-geoelectric cross section model was developed to evaluate the ground water potential for the qualitative and quantitative assessment of ground water potential zones. Shallow aquifer zones of

30


Fig. 1 Location and Geological Map of the study area, Beodnabad catchment

Fig. 2 GPR profiles from the study area showing different layers and features

31


thickness 15-25 meter occur at places aquifer thickness exceeds more than 50 meter owing to fracturing in synclinal valley. Thus, the ground water existing in the fractured rocks constitutes the productive water bearing zones. Based on the VES results, there are four geo-electrical layers. The integrated results of GPR and VES have shown that top layer has a resistivity of more than 7 to 196 Ω.m with a thin thickness of 2 to 8 meter. The upper part of top layer mainly comprised of clayey to sandy silt up to 0.5-2.5 meter depth and beneath it an approximately 5 meter thick zone lying comprised of rock pieces with clayey sand and silt. While the second layer comprised of fractured formation with a thickness range 10 to 35 meter of resistivity range 300-555 Ω.m (Table 1). The third layer comprised by a massive basement rocks and the depth to the basement generally varies from 25 to 35 meter but sometime the depth exceeds more than 70 meter due to the presence of a thick sedimentary deposition in the adjoining area of thrust/faults. Based on the geoelectrical and structural parameters a ground water potential map was prepared, in which good, moderate, and poor ground water zones were demarcated. Based on the fractured density and GPR reflection of the subsurface, 3 to 4 GPR layers have been derivated for the entire study area. On the basis of number of fractures and fractured layer thickness, the area categorized as potential aquifer zone for the ground water development and management. Generally, the upper layer varies with the thickness from 2-4 meter act as over burden with unsaturated properties. This layer assumes hydrologically important while recharging the aquifer and constitutes by clay to weathered and semi weathered formations of highly porous inevitably. While second layer generally acts as saturated layer and have thickness range of 15-40 meter shows higher fracturing trends. The third layer generally strike after 30-50 meter generally this layer comprised by massive rocks while some time in faulted zones this depth reaches more than 60 meters, generally these zones have forth layer which act as basement rocks with this condition most of places shows the existence of deep productive aquifers. Thus the integrated geophysical techniques and borehole lithologs has enabled to identify the fractures and various hydrogeological settings. Further, the integrated results has also enabled to prepare a comprehensive ground water development and management plans for Beodnabad catchment area and thus this integrated techniques involving GPR and VES have proved its efficacy in this art of investigations.

Table 1. Geoelectrical parameters interpreted from resistivity sounding data of Beudnabad catchment

32


Fig. 3 Geo-electric section along the traverses A-A’ and B-B’

Fig. 4 Structural and Litho-Geoelectric section along traverses A-A’ and B-B’

33


5 Conclusion The integrated study by GPR and VES technique has judiciously determined and is utile and beneficial for conducting hydro-geological studies in deciphering and accessing the ground water potential zones for its development and management with greater accuracy. The thickness of unsaturated zones varies, generally up to 3 to 4 meter. The ground water tends to occur in shallow depth of resistivity ranges 30-554 Ω.m. and the depth varies from 10 to 40 meter at suitable locales. The ground water occurrence is limited to very shallow depth while the depth in faulted/fractured zone is quite deep. Hence, pinpointing ground water is crucial for the sustainable development of this island due to its strategic locality. Therefore, plausible exploration and development plans should be taken carefully. Further, the ground water resources of the Beodnabad catchment are safe and not exploited so far.

References Bayer P, Huggenberger P, Renard P, Comunian A (2011) Three-dimensional high resolution fluvioglacial aquifer analog: Part 1: Field study. Journal of Hydrology 405:1-9. Benson AK (1995) Application of GPR in assessing some geological hazards – examples of ground water contamination, faults, cavities. Jour Appl Geophy 33:177-193. Beres MJ, Haeni FP (1991) Application of Ground-Penetrating-Radar Methods in Hydrogeologic Studies. GROUND WATER 29:375-386. Buselli G, Kanglin L (2001) Ground water contamination monitoring with multichannel electrical and electromagnetic methods. Journal of Applied Geophysics 48:11-23. Cook JC (1975) Radar transparencies of mines and tunnel rocks. Geophysics 40:865-885. Daniels JJ, Roberts R, Vendl M (1990) Ground penetrating radar for the detection of liquid contaminants. J Appl Geophys 33:195-207. Davis JL, Annan AP (1989) Ground penetrating radar for high-resolution mapping of soil and rock stratigraphy. Geophysical Prospecting 37:531-551. Deceuster J, Delgranche J, Kaufmann O (2006) 2D cross-borehole resistivity tomographies below foundations as a tool to design proper remedial actions in covered karst. Journal of Applied Geophysics 60:1041-1070. Deparis J, Fricout B, Jongmans D, Villemin T, Effendiantz L, A. M (2008) Combined use of geophysical methods and remote techniques for characterizing the fracture network of a potential unstable cliff site (the “Roche du Midi”, Vercors massif, France). Journal of Geophysics and Engineering 5:147-157. Doetsch J, Linde N, Pessognelli M, Green AG, Günther T (2012) Constraining 3-D electrical resistance tomography with GPR reflection data for improved aquifer characterization. Journal of Applied Geophysics: 68-76. Doolittle JA, Jenkinson B, Hopkins D, Ulmerd M, Tuttlee W (2006) Hydropedological investigations with ground-penetrating radar (GPR): Estimating water-table depths and local ground-water flow pattern in areas of coarse-textured soils. Geoderma 131:317–329. Edet AE, Okereke CS (2002) Delineation of shallow ground water aquifers in the coastal plain sands of Calabar area (Southern Nigeria) using surface resistivity and hydrogeological data. Journal of African Earth Sciences 35:433–443. Ezersky M (2008) Geoelectric structure of the Ein Gedi sinkhole occurrence site at the Dead Sea shore in Israel. Journal of Applied Geophysics 64:56–69. Flathe H (1955) Possibilities and limitations in applying geoelectrical methods to hydrogeological problems in the coastal areas of northwest Germany. Geophys Prospect 3:95-110.

34


Goldman M, Neubauer FM (1994) Ground water exploration using integrated geophysical techniques. Surv Geophys 15:331-361. Greenbaum D, Carruthers RM, Peart RJ, Shedlock SJ, Jackson PD, Mtetwa S, Amos BJ (1993) Ground water exploration in southeast Zimbabwe using remote sensing and ground geophysical techniques. WC/93/26. British Geological Survey, Keyworth, Nottingham. p 10. Khalil MH (2010) Hydro-geophysical configuration for the quaternary aquifer of Nuweiba alluvial fan. J Environ Eng Geophys (JEEG) 15:77–90. Koefoed O (1979) Geosounding principles I, Resistivity sounding measurements. 1st ed. Elsevier, Amsterdam, The Netherlands. Loke MH, Barker RD (1996) Rapid least squares inversion of apparent resistivity pseudosections by a quasi-Newton method. Geophysical Prospecting 44:131– 152. Maury S (2012) Strategies on Ground water Resources Management and Development of South Andaman Islands, India - An Extensive Approach of Remote Sensing and Ground Penetrating Radar (GPR). National Conference on Quest for Advancements in Civil Engineering (QACE' 12). SRM University, Chennai. pp 506-514. Maury S, Balaji S (2014) Geoelectrical method in the investigation of ground water resource and related issues in Ophiolite and Flysch formations of Port Blair, Andaman Island, India. Environ Earth Sci 71:183-199. McDowell PW (1979) Geophysical mapping of water filled fracture zones in rocks. International Association of Engineering Geology Bulletin 19:258-264. McNeill JD (1980) Electrical conductivity of soils and rocks. technical note TN-5. Geonics Limited, Mississauga. Olson CG, Doolittle JA (1985) Geophysical techniques for reconnaissance investigations of soils and surficial deposits in mountainous terrain. Soil Sci Soc of Am Journal 49:1490-1498. Oyedele KF, Ayolabi EA, Adeoti L, Adegbola RB (2009) Geophysical and hydrogeological evaluation of rising ground water level in the coastal areas of Lagos, Nigeria. Bull Eng Geol Environ 68:137– 143. Parasnis DS (1997) Principles of applied geophysics. Chapman & Hall, London. Park YH, Doh SJ, Yun ST (2007) Geoelectric resistivity sounding of riverside alluvial aquifer in an agricultural area at Buyeo, Geum River watershed, Korea: an application to ground water contamination study. Environ Geol 53:849–859. Parker R, Ruffell A, Hughes D, Pringle J (2010) Geophysics and the search of freshwater bodies: A review. Science and Justice 50:141–149. Pellicer XM, Gibson P (2011) Electrical resistivity and Ground Penetrating Radar for the characterisation of the internal architecture of Quaternary sediments in the Midlands of Ireland. Journal of Applied Geophysics 75:638–647. Rubin LA, Fowler JC (1978) Ground-probing radar for delineation of rock fractures. Eng Geol 12:163170. Sandberg SK, Slater LD, Versteeg R (2002) An integrated geophysical investigation of the hydrogeology of an anisotropic unconfined aquifer. Journal of Hydrology 267:227–243. Taylor RW (1982) Evaluation of geophysical surface methods for measuring hydrological variables in fractured rock units. H0318044. U.S. Bureau of Mines Research. p 147. Ulriksen CPF (1982) Application of impulse radar to civil engineering. Lund University of Technology. Zohdy AAR (1969) The use of Schlumberger and equatorial soundings in ground water investigations near El Paso, Texas. Geophysics 34:713-728.

35


Impact Assessment of Integrated Water Resource Management through Farmers Participatory Action Research Programme (FPARP) in Andaman and Nicobar Islands A. Gayen1, A. Zaman2, A. Kar 3, S.K. Ambast 4 and N. Ravisankar 5 1,3

Central Ground Water Board Bidhan Chandra Krishi Viswavidyalaya 4,5 Central Agricultural Research Institute, Port Blair, A&N Islands E-mail:[email protected] 2

Abstract A great deal of works was carried out both in pre and post-tsunami periods depending upon heterogeneous agro-climatic conditions, geomorphology and hydrogeology with undulating topography. The Farmers Participatory Action Research Programme (FPARP) was initiated to demonstrate the four technologies namely - (i) Crop diversification through broad bed and furrow (BBF) system, (ii) Pond based integrated farming system (IFS), (iii) Tank-well system (TWS) and (iv) Introduction of micro-irrigation system (MIS) for the purpose of effective utilization of groundwater in South Andaman, Little Andaman, Havelock and Neil Island in the farmers’ fields. The impact assessment of these technologies has been evaluated in finding out the additional benefit over the conventional method as well as to uplift the socio-economic status of the end users. On-station tested technology on BBF envisaged efficient crop rotation, land utilization and nutrient management growing vegetables and rice crop together with proper utilization of water resources in the low-lying waterlogged situation, wherein the lands were neither cultivating any crop nor used for any other purpose earlier carried over to on-farm. The farmers became interested on vegetable cultivation on the beds and fish culture in the furrows. Thus, vegetable crops used to fetch more earning in the Islands during monsoon season. The commonly grown vegetables were okra, brinjal, chilies, bitter gourd, amaranthus, radish and pumpkin. The net returns from vegetable cultivation in beds ranged from Rs. 67091/ha to as high as Rs.89000/ha depending upon the management of crop. Pond based integrated farming system (IFS), rainwater harvesting and tank-well system also proved beneficial to grow more than one crop in a year. The results of demonstration on introduction of micro irrigation for crop cultivation also revealed that adoption of water conserving technologies proved more profitable proposition in sustainable crop production.

Key words: FPARP, Water management, Rain water harvesting Technology, Impact assessment.

INTRODUCTION Andaman and Nicobar islands is blessed with copious rainfall and has typical geomorphologic set up and complex geology and hydrogeology, which are responsible for formation of un-ubiquitous potential groundwater reservoirs. Low productivity is attributed to non-availability of water particularly post-monsoon season wherein lack of proper drainage in the low lying valley areas. One of the effective ways to increase crop production especially growing vegetable crops is to cultivate vegetable during monsoon period by manipulating the land configuration. The system is commonly known as raised beds and sunken furrows (RBSF), which alternatively called as broad beds and furrow system (BFS) to provide proper drainage to suit the cultivation of vegetables on broad beds and to provide standing water for growing rice in furrows. Such other technologies like pond based integrated farming system (IFS), tank well system (TWS) and introduction of micro irrigation system to increase water productivity and crop water efficiency. Participatory approach in technologies dissemination at faster rate could only bridge up the gap between the technology generation and adoption. Adoption of proven water management technologies ensures to achieve high water productivity in agriculture.

36


Trist (1980) considered the irrigation system as a complex socio-technical phenomenon that involved interaction between physical, environmental and technological parameters in the process of adoption. Whyte (1991) considered the participatory action research as more effective and communicative measures in the developmental processes. Korten (1980) described the participatory action research as a method of merging both developmental intervention and research activities as an effort to involve the users in systemic process of change to make the socio-technical system more effective and efficient. Xianjun (1996) reported that on-farm irrigation management and irrigation service thereby improved by involving farmers in water management practices and introducing an acceptable water-saving irrigation schedule for growing crops and increasing agricultural production. Pramanick and Mallick, (1996) described on-farm participatory field trials brought positive improvements towards better water use efficiency following the recommended methods of water management practices in the farmers field in Damodar Valley Corporation (DVC) command in West Bengal. Dhindwal and Poonia (1994) also reported the success story of on-farm water management. Gayen and Zaman, (2013) stated the adoption of rainwater harvesting with existing ponds ensured more water resource availability and utilization in coastal saline region of Sagar Island. Under this stated situations, 4 (four) proven water management technologies were considered for demonstration in farmers field for growing crops in Andaman & Nicobar Island to combat water scarcity ensuring effective water resource utilization.

MATERIALS AND METHODS Selection of crop(s) and crop sequence(s) also played an important role for enhancement of water use efficiency. Conservation, distribution and utilization of irrigation water are the basic parameters of on-farm water management. Optimum scheduling of irrigation, suitable method adoption, and conjunctive use of rain water, surface water and ground water for crop cultivation along with provision of drainage are the pre-requisite for optimum water management. Application of proper amount of water at proper time increased the water use efficiency and crop yield maximization. Scheduling of irrigation with limited water availability is a big challenge to the irrigation experts that needs rigorous research. In this context, the following technologies were considered for adoption in Andaman & Nicobar Island through Farmers’ Participatory Action Research Programme (FPARP) with 50 (fifty) field demonstration growing crops at various locations/villages (Table-1).

Table 1: Technology details for demonstration under FPARP Technology Broad bed and furrow system (BBF) Pond based integrated Farming System (IFS) Tank Well System

No. of demonstration 15

15 10

District of Adoption South Andaman, Middle & North Andaman South Andaman, Middle & North Andaman South Andaman

37

Locations/Villages Calicut, Maccapahar, Burmanalla, Beodnabad, Tushnabad, Hazaribagh, Chouldari, Wandoor, Little Andaman, Ragat & Dijlipur Sippighat, Guptapara, Wanddor, Little Andaman, Neil Island, Havelock Island, Rangat& Dijlipur Rangachun, Maccahad, Dandus point,


No. of demonstration

Technology

District of Adoption

(TWS) Micro Irrigation System (MIS)

10

South Andaman

Locations/Villages Mamyo, Tirur, Badmaspahad, Calicut Calicut, Maccapahad, New Bimblitan, Nayashahar, Tushnabad, Mathura & Hut bay

RESULTS AND DISCUSSION Four technologies viz. broad bed and furrow system (BBF), pond based integrated farming system (IFS), tank-well system (TWS) and micro-irrigation system (MIS) have been implemented in 50 farmers’ field. The impacts of these technologies were enlisted as stated hereunder (Table 2).

Table 2: Impact of different technologies implemented in the farmers field I. Broad bed and furrow (BBF) system Sl. No.

Item

Conventional method WUE in rain fed rice –fallow : Rs 3 0.80/ m

WUE in BBF : Rs 10.80/m

1

Water saving (m /ha)/ water use efficiency (WUE) Yield (mention crop)

Rice

Rice + vegetables + Fish

Main product (kg/ha)

Rice: 2000 kg

Rice: 1500 kg (in 4500 m area) 2 Vegetables: 6500 kg (4000 m area) Fish: 150 kg (Out of 12 farmers, only 2 farmers have taken up rice in furrows while 3 farmers have utilized the sloppy area of furrows for growing) creeper vegetables

Crop diversification for growing hi value vegetables during monsoon season & in-situ rain water harvesting

By-product (kg/ha)

Rice straw: 3000 kg

Rice straw: 2000 kg, Vermi-compost: 3500 kg

Recycling of waste

3

2

Using Technology(ies)

Benefits 3

2

In-situ rain water harvesting and increased cropping intensity with fish

Inputs (kg/ha) Seed

40 kg

3

4.

5.

Fertilizer

-

Pesticide

-

Financial benefits from agriculture, fisheries & livestock etc.

Rs 23000

Other benefits e.g. Ecological gains etc., if any

-

Rice : 40 kg Vegetables: 75 kg Fingerlings: 150 no’s Vermi-compost (3500 kg) -

-

Rs 325000/=

Enhanced income from high value vegetables and fish during monsoon season

Round the year employment and income generation

Insurance against failure of mono-crop

38


II. Pond based integrated farming system (IFS) Sl. No.

Yield (mention crop)

Conventional method WUE in mono culture (Fish) : 3 Rs 41.6/m Fish


Fish 750 kg

By-product (kg/ha)

-

Item 3

Water saving (m /ha)/ water use efficiency

1

2

Inputs (kg/ha) Seed

3

4.

5.

Fingerlings (1000 no’s)

Using Technology(ies) WUE in IFS (Integration of crops, animal and fish in the 3 pond): Rs 79.4 /m Fish Crops (vegetables & field crops) Poultry (Nicobari fowls) Goats (Black Bengal) Ducks (Khaki Cambell) Fish : 750 kg Crops : 2150 kg Poultry & duckery: 150 kg meat + 3000 eggs Goats: 30 kg Vermicompost: 3500 kg

Benefits Multiple use of water for crop/ animal and fish Multi-crop system

50-100% increase in arecanut yield + additional income from black pepper Availability of organic manure -

Fertilizer

-

Fingerlings (1000 no’s) Crops : 5 kg Poultry : 50 no’s Ducks: 25 no’s Goat: 2 no’s Vermi-composting

Pesticide

-

Vermi-wash

Monetary benefits from Agriculture, fisheries & livestock etc. Other benefits e.g. Ecological gains etc., if any

Rs 75000

Rs 142900/ ha

Enhanced farm income from different sources

-

Recycling of output of one system to other as input reduced soil and water degradation

Ecologically sustainable system


Benefits

Recycling of animal wastes to crops through vermicomposting Biological control of pest & diseases

III. Tank Well System (TWS) Sl. No.

Item 3

1

Water saving (m /ha)/ water use efficiency Yield (mention crop) Main product (kg/ha)

2 By-product (kg/ha) 3

Inputs (kg/ha) Seed

Conventional method Rainfed Mono-cropping Rice Rice: 2000-3000

3

15.7 m /day Water resource creation Rice, Vegetables

3

15.7 m /day Double cropping Additional yield of Ladies finger

Rice straw: 3000-4000

Rice: 2000-3000 Ladies finger: 5000-6000 Rice straw: 4000-5000

Paddy seeds (40 Kg)

Paddy seeds (40 Kg), Saplings of black pepper

-

39


Sl. No.

4

5

Item

Conventional method

Fertilizer

N:P:K::90:40:60

Pesticide

-

Monetary benefits from agriculture, fisheries & livestock etc. Other benefits e.g. ecological gains etc., if any

-


Benefits

(1200 Nos/ha) Paddy: N:P:K::90:40:60 Ladies finger: Ladies finger: Hamla (1.5 l/ha) Additional income from black pepper plantation

-

Additional income of Rs 25000-30000/ ha

IV. Micro Irrigation System (MIS) Sl. No.

Item 3

Water saving (m /ha)/ water use efficiency Yield (mention crop)

1

2


Conventional method -

4

5

Benefits

-

Up to 75%

Rainfed areca nut and banana

Irrigated areca nut and banana

Black pepper be planted on areca nut

Areca nut: 2000

Areca nut: 3000-4000

50-100% increase in areca nut yield + additional yield from black pepper -

By-product (kg/ha) Inputs (kg/ha) Seed Fertilizer Pesticide Monetary benefits from agriculture, fisheries and livestock etc. Other benefits e.g. ecological gains etc., if any

3


-

-

-

Saplings of black pepper NPK Additional income from black pepper plantation

-

Judicious use of water resources

Additional income of Rs 25000-30000/ ha

-

Table 3: Cost of each technology (ies) (Rs./ha) Sl. No. 1 2

Technology

Cost (Rs)

Broad bed and furrow system (BBF) Pond based integrated farming system (IFS)

Rs 50000 for 0.2 ha land (Pump set cost is borne by the farmers) Rs 50000 (Crop husbandry + poultry cum duck shed + fisheries + vermi-composting; (Wood for shed is borne by the farmers) Rs 50000 (for 2 m dia CC rings for 5 m depth well + inputs; (Digging of well is done by the farmers) Rs. 50000 for 0.20 ha land plantation (Shade for pumping unit and trenching is done by the farmers)

3

Tank-Well System (TWS)

4

Micro-irrigation System (MIS)

The FPARP project has became as an instrumental platform to implement different interventions in the farmers’ field. These technologies have been discussed with each of the selected farmers. Considering their land situation and their priority for technologies, options of interventions

40


have been finalized. Farmers in Little Andaman islands did sowing of bitter gourd and bottle gourd on the slopes of beds and made machan over furrows thus saving a space of beds for other vegetables besides utilizing the vertical space of furrow. Machan over furrow also provides shade to fishes in furrows whenever there is high temperature. Other farmer in Indiranagar had grown okra as first crop in beds and planted cowpea near to okra when it is in maturity and trailed over stalk of okra thus saved cost of preparation of land and labour cost for putting sticks to cowpea. Around 75% of the farmers are willing to extend their area under BBF in waterlogged areas. In the villages, where in the technology was demonstrated, many farmers were willing to adopt the technology with provision of bearing the partial making cost of BBF is Rs.50000/ha to Rs.65000/ha using excavator. Assessment of impact of the pond based IFS has been taken up in farmers field at South Andaman Island. Gross return from 0.2 ha area ranged from Rs.12000 to Rs.40000/- depending upon the components such as vegetables, goat, poultry and duckery integration. Similarly, net return was more wherever vermin-compost production was made by the farmer himself. Farmer of Mile Tilak village made self production of vermin-compost and applied to the crops through which he received Rs 18000/- as net return from 0.2 ha of pond based IFS. The net return per rupee invested ranged from 0.6 to 2.8 while average net productivity of Rs 35.1/day can be obtained by adopting pond based IFS in 0.2 ha area. Few farmers have adopted their own innovative practices during the demonstration. A farmer from Netaji Nagar of Little Andaman made vermin-compost cum verminwash unit from the RCC rings supplied for making of vermin-compost. Vermi-wash is sprayed to vegetables after enriching with Trichoderma and Pseudomonas for control of pest and diseases. The socio-economic status has been improved substantially on adoption of these technologies through participatory approach. Acknowledgement: The authors show their earnest gratitude to Shri G.C.Pati, Regional Director, Central Ground Water Board, Eastern Region, Kolkata for according kind permission to publish this paper in the workshop at Port Blair, A&N Islands.

References Dhindwal, A.S. and Poonia, S.R. 1994. On-farm water management – A success story. Intensive Agriculture. 32(1-2) 37-38 Kurten, D. 1980. Community Organization and Rural Development: A Learning Process Approach. Administrative Review, 40 (Sept-Oct): No.5 Pramanick, M. and Mallick, S. 1996. Farmer’s participatory approach for improvement of present status of irrigation water utilisation in DVC canal Command. Proc. of ICID/FAO Workshop, Rome, Water Report 8 Trist, E. 1980. The evaluation of Socio-technical system: A conceptual framework and Action Research Programme. Toronto. Xianjun, C. 1996. Introduction of water saving irrigation scheduling through improved water delivery: a case study from China. Proc. of ICID/FAO Workshop, Rome, Water Report 8; Whyte, W.F. 1991. Participatory Action Research. Newbury Park. California; London & New Delhi, Sage Publications. Gayen, A. and Zaman, A. 2013. Mitigation of water crisis and growing crops in lean period by rainwater harvesting through concreted rooftops and household ponds in Sagar Island. Current Agril Res. J. 1 (2): 87-91.

41


Rainwater Harvesting for Productivity Enhancement of Degraded Coastal Areas A.Velmurugan*, T.P.Swarnam, T.Subramani, S.Swain, M.S.Kundu, Nagesh Ram, Subhash Chand, Sankaran, M., and S. Dam Roy Central Agricultural Research Institute, Port Blair-744 101 * Corresponding author: [email protected]

ABSTRACT The great challenge in the near future will be the task of increasing food production with less water from the available land. The situation was worsened in Andaman island due to the intrusion of sea water during tsunami which made the soil condition unfavorable for immediate crop cultivation. Hence, in the present study an attempt was made to evaluate the impact of broad bed and furrow system in harvesting rainwater and improving the water productivity at farmers field in the degraded 3 -1 coastal areas. The results showed that the system can harvest and store nearly 4476 m ha of rainwater. Under island conditions 67 % of the rainfall was used by the crops while 14% and 19 % were lost in the form of evaporation and deep percolation respectively. The system also provided ample scope for crop diversification and the cropping intensity increased upto 190 – 220 %. The 3 water productivity was high at 47.36 Rs/m . The integration of crops along with fish in the BBF will ensure increased farm income and sustainable livelihood security in coastal degraded areas. Key words: Rainwater harvesting

INTRODUCTION National food security and livelihood security are key development indicators which mainly dependents on limited land resources. This can be achieved in favorable agro-ecologies through the introduction of improved varieties, increased use of inputs, and expansion of irrigation. Though, India still has one of the lowest land productivities (1.7 t/ha) among the major food-producing countries such as China (4.0 t/ha) and USA (5.8 t/ha). Doubling land productivity in five decades from now could help India to meet most of its increasing food demand. But over the years water has become a scare resource and hence the water productivity should be enhanced which requires determined efforts and technology. Crop water productivity is the amount of water required per unit of yield and a vital parameter to assess the performance of irrigated and rainfed agriculture (IWMI, 2001). Crop water productivity will vary greatly according to the specific conditions under which the crop is grown.

The great

challenge for the coming decades will be the task of increasing food production with less water, particularly in countries with limited water and land resources. Conservation of available water resources and improvement of crop water management is the key to optimize crop production with limited and dwindling water supplies (Kijne, 2003). This can also be achieved through rainwater harvesting and its proper utilization for crop production. In Andaman Islands after the December 2004 tsunami, the sea water intrusion changed the soil conditions and turned it to be unfavorable for immediate crop cultivation. The EC of tsunami affected soils varied between 6.7 dS/ m and 23.7dS/m and over the years though the salinity has decreased but the problem of water logging remains. The area under degraded land and water are

42


increased after tsunami. Therefore, it is imperative to develop a technique to address the issue of land and water degradation. Broad bed and furrow system holds promise as the system helps to harvest the rainwater as well as to utilize the land effectively which increases the water productivity. Hence, in the present study an attempt was made to evaluate the impact of BBF at farmers field in the degraded coastal areas of Andaman islands in harvesting rainwater and improving the water productivity.

STUDY AREA Andaman and Nicobar Islands receive an average annual rainfall of about 3100 mm (Fig. 1). Nearly 95% of annual rainfall is received during May to December (2300 mm in May- September during Southwest monsoon and 650 mm in October-December during Northeast monsoon). Because of this most of the coastal low lying areas suffers from water logging ranging from 40 -120 cm. In contrast, the remaining 4 months from January to April is dry period when the numbers of rainy days in each month hardly exceed three. Agriculture badly suffers during this period due to moisture stress which necessitates the need to improve the water productivity through various suitable methods. The situation was aggravated by the December 2004 tsunami which caused the stagnation of sea sediments, debris and sea water. The thick slushy black deposits on the soil surface causing heavy damage to the soil structure and standing crop. Rainwater harvesting and use is the only scope for such areas to improve the land and water productivity while ensuring the livelihood for the people.

600

25

21

21

20 Rainy days

Rainfall (mm) & Evaporation (mm)

19

20

Rainfall (mm)

17 400

Evaporation (mm)

15

15 13 300

Rainy days

500

10 200

7

4

100

5

3 2 1

Wet season

April

March

Febraury

January

December

November

October

September

August

July

June

0 May

0

Dry season Season and months

Fig. 1. Rainfall, evaporation and number of rainy days in Andaman Islands Broad Bed and Furrow system The land shaping technique of BBF in the coastal affected land and other suitable location may results in the increased water productivity and livelihood security. The BBF system is most appropriate for monocropped rice and low lying area where water logging is a major problem. The purpose of this land manipulation technique is to bring the water logged and degraded area under cultivation utilizing the monsoon rain for reclamation and water harvesting (Ravisankar et al., 2008).

43


Fig. 2. Schematic diagram of BBF system The design and dimension of BBF system (Fig. 2) was developed depending upon certain parameters including intensity of rainfall, physical and chemical properties of soil and drainage requirement. This system involves making of broad bed and furrow alternatively in rice fields. Broad beds are made in the shapes of inverted trapezium by digging soil from either sides of the broad bed and putting it in the bed area by cut and fill method. The proper time of starting the earthwork is summer season because in this season the soil can be easily manipulated. It was found that beds of 4-5 m width and furrow of 5-6 m width with minimum 1 m depth are found suitable for the island conditions having high intensity rainfall. The length and breadth of beds and furrows can be adjusted depending on the availability of land. Therefore, in 1 ha of agricultural field, 10 beds of 4 m x 100 m x 1 m and 10 furrows of 6 m x 100 m x 1 m can be made. For a small holding 60 m x 40 m is optimal size. High value vegetables can be grown on beds during monsoon seasons and paddy + fish can be practiced in furrows. A total of 10 systems were made in the farmer's field in South Andaman Island which was evaluated for its performance.

RESULTS AND DISCUSSION Diversification of the traditional farming in the coastal areas has a tremendous scope. The present system of mono-cropping with rice offers only sub optimal resource utilization and instead of rice in Kharif, paddy + fish was grown in the furrows. During monsoon season, furrows were used for rice and fish cultivation while vegetable/ fodder crop was cultivated on raised beds. During post monsoon season, vegetables and pulses were grown on the raised beds. The use of BBF reduced the average annual runoff to one half and the soil loss to one forth as compared to that of the traditional 3

-1

system. The system can harvest and store nearly 4476 m ha

of rainwater. By adopting this

system, nearly 67 % of the rainfall was used by the crops while 14% and 19 % were lost in the form of evaporation and deep percolation respectively. This system is also useful in decreasing runoff and increasing infiltration (Fig. 3).

44


Fig. 3. Rainwater harvesting and vegetable cultivation in the BBF

The analysis revealed that productivity of BBF system made in water logged soil was highly significant than BBF in acid saline condition (pNa >K in all the samples tested. The pH of the water samples across the islands varied from 7.4 to 7.9 with mean value of 7.6 with carbonates mainly in the form of HCO3 . The classification of water based on WHO(1993) and ISI (1991) standards indicates that the water is fresh water type as the TDS is less than 500ppm. Only temporary hardness caused by bicarbonate results classification of the water in moderately hard to hard category.

INTRODUCTION Water quality refers to the chemical, physical and biological characteristics of water. It is a measure of the condition of water relative to the requirements. Water quality assessment is important because poor water quality can pose a health risk for people and also for the ecosystem. In addition, long term use of poor quality water for irrigation will reduce soil fertility and crop production. Anthropogenic influences (urban, industrial and agricultural activities, increasing exploitation of water resources) and natural processes (changes in precipitation, erosion, weathering of crustal materials) degrade water resources and impair their use for drinking, industrial, agricultural, recreation or other purposes (Carpenter et al., 1998; Jarvie et al., 1998). Because lakes, reservoirs and rivers constitute the main inland water resources for domestic, industrial and irrigation purposes, it is imperative to prevent and control water pollution and to have reliable information on water quality. The evaluation of water quality in most countries has become a critical issue especially due to concerns that freshwater will be a scarce resource in the future (Singh et al., 2004).Water quality monitoring is a helpful tool not only to evaluate the impacts of pollution sources but also to ensure an efficient management of water resources (Strobl and Robillard, 2008). Water is one of the most critical resource and constraint in an Island ecosystem where only rainfed agriculture is prevalent. There is very limited scope for development of large scale reservoir, drainage system or canals in these Islands due to flat topography, lack of well developed surface water system as the region is in the active tectonic belt experiencing subsidence and uplift besides topographic features where central high land is surrounded by coastal plain, and in some cases undulating terrain with the mountain chain along the length of the island. The surface water sources

55


include only ponds and small streams draining only during monsoon season. The major ground water sources are the porous formation consisting of beach sand with coral rags and shells, the thin cover of alluvial or colluvial deposits in the coastal or intermountain valleys and adjoining foot hills besides fractured volcanic and igneous rocks. However, the ground water resources were not well developed in these islands (Central Ground water board 2010). Hence, the surface water plays an important role in sustaining life in these islands and assessment of water quality for domestic and other purpose is imperative. As there is no such systematic study, attempt was made to assess the quality of surface water resources from major inhabited islands of Nicobar Islands.

MATERIAL AND METHODS The Nicobar Islands are situated in the South-east of the Bay of Bengal between 6° - 10° N latitude and between 92° - 94° E longitude and sepa rated from the Andaman group by 10° channel. The Nicobar Islands are part of a great island arc created by the collision of the Indo-Australian Plate with Eurasia. The islands enjoy tropical humid climate because of their location in equatorial zone surrounded by Andaman Sea. The islands receive rainfall from both the south west and north east monsoons and maximum precipitation is between May & December. On an average the rainfall is received in 142 rainy days with the maximum occurred in June and November. However, there is also water deficit period which extends only for 3 to 4 months from January to April. The mean annual temperature ranges from 23 to 30° C. Rainfall is he avy due to annual monsoons and measures around 3000 to 3800 mm each year. The data of past ten years showed that the mean relative humidity is 79%, and the maximum and minimum temperature is of 30.2° C and 23.0° C, respectively.

In study

the

present

surface

water

samples from ponds and streams from

were

collected

different

during

Islands

November

December

2013.

to From

each island five samples were collected in sterilized 1

lit

high

polyethylene

density containers.

The collected samples were transported to laboratory in ice box and stored at 4° C and analyzed for various quality parameters as per standard procedure (APHA 1998). The samples were analyzed for pH, electrical conductivity, total alkalinity, total hardness, total dissolved solids, nitrate nitrogen, chloride, sodium, potassium, calcium, magnesium and total coliform.

56


RESULTS AND DISCUSSION Water quality parameters The surface water quality parameters for different Islands were presented in Table 1. The chemical composition of the surface water samples in the islands showed not much variation. The EC values of the region varied from 250 to 860 µS cm

-1

-1

with mean value of 497 µS cm . The mean

values of TDS across the islands varied from 256 to 409ppm. As per TDS classification, all the water samples were classified as fresh water type with values ranging from 160 to 476 ppm (Freeze and 2+

Cherry 1979). Among the dissolved ions, Ca

2+

and Mg

predominates the cation concentration with

values ranging from 37 to 53 ppm and 13.2 to 30.3 ppm respectively. The composition of cations were 2+

2+

+

+

-

in the order of Ca > Mg >Na >K in all the samples tested. Among the dissolved anions HCO3 and -

Cl dominates the anion concentration with mean values ranging from 84.6 to 133.2 ppm and 32.8 to 2-

137.8ppm respectively. The concentration of CO3 , nitrate and sulfate ion concentration was less in all the samples. The pH of the water samples across the islands varied from 7.4 to 7.9 with mean -

value of 7.6 indicating that the dissolved carbonates are mainly in the form of HCO3 (Adams et al. 2000) which was also evidenced from individual ionic composition of water samples. The nitrate concentration was very low (1.5 + 1.2 ppm) as there is no scope for contamination from agricultural sources where only natural farming and no chemical inputs are applied.

EVALUATION OF WATER QUALITY Based on the analytical results, the suitability of the water samples for domestic and agricultural usage was evaluated based on the World Health Organization (WHO 1993) and Indian Standards (ISI 1991). The water samples are within the permissible limit as prescribed by both WHO and ISI standards (Table 2). As per the WHO (1993) standards all the water samples are within the acceptable limit except for total hardness which exceeded 100ppm but falls within the maximum allowable limit of 500ppm. However as per the ISI (1991) standards all the parameters are within the highest desirable prescribed for each parameter indicating that the water resources of the Nicobar islands are still pristine and highly suitable for domestic consumption without much treatment. Similarly, according to Freeze and Cherry (1979), Davies and DeWeist (1966), the water in these Islands are classified as freshwater type based on TDS and are desirable for drinking purpose. Hardness is an important criterion for determining the suitability of water for various purposes viz., domestic, drinking etc. Hardness may be temporary due to carbonate and bicarbonates or permanent due to sulfate and chlorides of calcium and magnesium. In the study region total hardness ranged from 54.4 to 349.4ppm and is classified as moderately hard to hard (Table 3). And they are suitable for domestic use as per WHO and also ISI standards and are mainly of carbonate and bicarbonate type constituting only temporary hardness which may affect the taste and cause scale formation in pipes. Magnesium is one of the constituent for hardness of water and higher magnesium may be cathartic and diuretic (WHO 1997). Besides, the magnesium combined with sulfate act as laxative to 2+

human beings. In these islands, the mean values of Mg

concentration varies between 13.2 to

30.3ppm and most of the samples are within the desirable limit as per ISI (1991) standards. The sulfate concentration was very low ranging from 1.2 to 2.1ppm and falls within the recommended

57


limits. The nitrate concentration was very low (1.5 + 1.2 ppm) mainly because there is no scope contamination from agricultural sources as it is only natural farming and no chemical inputs are applied as in the case of intensive agriculture prevalent in other parts of India. The integrated suitability analysis by considering all the quality parameters indicated that the surface water in these islands are suitable for both domestic and agricultural purpose and the quality is comparatively better than in other parts of India or elsewhere.

CONCLUSIONS The surface water quality for drinking and domestic use was evaluated for major inhabited islands of Nicobar. The study indicated that the water is suitable for the above purpose. The calcium, magesium along with bicarbonates and chlorides predominates the ionic concentration. The nitrate as well as sulfate concentration was very low. The classification of water based on WHO(1993) and ISI (1991) standards indicates that the water is fresh water type as the TDS is less than 500ppm. Only temporary hardness caused by bicarbonate results classification of the water in moderately hard to hard category. This type of hardness affects the taste and sometimes clog the pipelines.

REFERENCE Carpenter, S.R., Caraco, N.F., Correll, D.L., Howarth, R.W., Sharpley, A.N., Smith, V.H.,1998. Nonpoint pollution of surface waters with phosphorus and nitrogen. Ecological Applications 83, 559–568. Central Ground water board 2010. Approach paper on ground water quality issues in Islands. Central Ground Water Board, Ministry of Water Resources, Government of India. Davies, S.N. And DeWiest,r.J.M.(1996). Hydrogeology.New York:Wiley. Freeze, R. A. and Cherry,J.A.(1979). Groundwater.Englewood Cliffs:Prentice Hall,pp.604. ISI, 1991. Indian Standard specification for drinking water.IS,10500,1-5. Jarvie, H.P., Whitton, B.A., Neal, C., 1998. Nitrogen and phosphorus in east-coast British rivers: speciation, sources and biological significance. Science of the Total Environment 210/211, 79– 109. Singh, K.P., Malik, A., Mohan, D., Sinha, S., 2004. Multivariate statistical techniques for the evaluation of spatial and temporal variations in water quality of Gomti River (India): a case study. Water Research 38, 3980–3992. Strobl, R.O., Robillard, P.D., 2008. Network design for water quality monitoring of surface freshwaters: a review. Journal of Environmental Management 87, 639–648. nd

WHO, 1993. Guidelines for drinking water quality, recommendations (2 ed). Geneva: WHO.

58


Table 1: Water quality parameters of surface water sources in different Islands Island Car Nicobar Katchal Kamorta

Mean /SD*

pH

EC

Mean

7.9

0.64

S.D

0.4

Mean

TDS (ppm)**

Ion concentration (ppm) 2+

2+

+

Na

K

+

2-

CO3

2-

TH***

74.2

1.8

165

1.9

58.7

1.3

58

84.6

2.6

166.8

0.6

253

-

HCO3

2-

Ca

Mg

409

37.0

18.2

14.2

7.1

0.4

85.8

2.1

0.16

102

15.0

6.4

8.6

6.9

0.9

46.5

7.9

0.43

256

53.0

30.3

10.0

15.3

1.4

-

SO4

Cl

NO3

S.D

0.2

0.06

38.4

6.8

2.5

3.7

3.4

1.3

27.2

2.4

70.6

0.9

18

Mean

7.4

0.40

256

51.3

13.2

7.5

6.9

0.0

104.5

1.5

32.8

2.2

181

S.D

0.2

0.14

89.6

33.1

8.6

3.7

5.8

0.0

58.7

2.4

12.8

3.2

88

Mean

7.9

0.50

320

39.4

18.7

16.8

7.4

2.4

133.2

1.2

137.8

2.2

173

S.D

0.3

0.07

44.8

5.6

4.3

2.9

6.9

2.6

57.9

1.3

42.2

0.8

22

Nancowry

* - Standard deviation, ** - Total Dissolved salts, ***-Total Hardness as CaCO3 Table 2: Classification of surface water based on WHO and ISI standards WHO (1993)

ISI (1991)

Water Highest Max quality Highest Max Parameter accept allowable desirable permissible limit limit (ppm) (ppm) (ppm) (ppm) TDS

500

1500

500

pH

6.5

8.5

6.5-8.5

TH (as CaCO3)

100

500

300

2+

75 50 45 200 200

200 150 200 12 600 400

75 30 45 250 200

Ca 2+ Mg + Na + K NO3 Cl 2SO4

Status of samples according to

WHO (1993)

2000 Within the acceptable limit (< than 500ppm) 6.5-9.5 Within the acceptable limit (pH 7.4 to 7.9) 600 Within maximum allowable limit (> 100 but