Project report on visit to Ethiopia to rapidly assess ...

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British Geological Survey

TECHNICAL REPORT WC/00/16R Overseas Geology Series DFID Project No. R7353

Project report on visit to Ethiopia to rapidly assess groundwater development issues in the Hintalo Wajerat Woreda (March 2000) J Davies and P D Menin

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Natural Environment Research Council

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Project report on visit to Ethiopia to rapidly assess groundwater development issues in the Hintalo Wajerat Woreda (March 2000)

J Davies and P D Menin

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British Geological Survey TECHNICAL REPORT WC/00116R Overseas Geology Series DFID Project No: R7353

Project report on visit to Ethiopia to rapidly assess groundwater development issues in the Hintalo Wajerat Woreda (March 2000) J Davies and P D Merrin

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This document is an output from a project funded by the Department for International Development (DFID) for the benefit of developing countries. The views expressed are not necessarily those of the DFID. DFID classification: Subsector: Water and Sanitation Theme: WI - Improve integrated water resources development and management, including systems for flood and droug ht control Project Title: Groundwater from low permeability rocks in Sub-Saharan AtTica Project reference: R735 3 Bibliographic: reference: Davies J and Merrin P D, 2000. Project Report on Visit to Ethiopia to Rapidly Assess Groundwater Development Issues in the Hintalo Wajerat Woreda (March 2000). BGS Technical Report WC/00/ 16C Keyword~:

Front cover illustration: Women collecting water in clay pots (einera) from a basalt/sandstone contact spring, Senale, Hintalo Wajerat Woreda, South Tigray

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© NERC 2000 Keyworth, Nottingham, British Geological Survey, 2000

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EXECUTIVE SUMMARY

As part of the DFID KAR programme studying the groundwater resources of geologically difficult areas in Sub-Saharan Africa, a two-man team from the British Geological Survey visited a proposed WaterAid project area in South Tigray, Ethiopia. Water supply is a major problem within the Hintalo-Wajerat Woreda, a rugged inaccessible area where the rural populations are some of the poorest in Ethiopia. The main NGO partners of WaterAid in the area, the Ethiopian Orthodox Church, have recently conducted a baseline survey of village level water resources in the area, including springs, wells and boreholes. They have submitted proposals for a programme of village water supply and sanitation inputs, works to be undertaken over a three-year period. WaterAid requested BGS to undertake a brief assessment of the water resources of the area using available data and field visits to provide an indication of survey, drilling and construction methods that need to be applied for their development. During March 2000, the BGS team visited much of the proposed project area. The geological formations present in the area that include limestones, sandstones, shales and interbedded basalt lavas and dolerite intrusions were studied. Typical village water sources including spring zones, wells and boreholes were also inspected. Discussions were held with Government and University Department staff and local NGOs in Makelle and Addis Ababa. Many data relating to the geology and hydrogeology of the area were obtained. The results of these visits and discussions were reported to the DFID representative and the WaterAid country representative in Addis Ababa. The BGS visit to the area was timely considering the current drought situation affecting the Horn of Africa region. The Geological Survey of Ethiopia in Addis Ababa and the Water, Mines and Energy Resource Bureau in Makelle both have a good understanding of the geology and hydrogeology of the Hintalo-Wajerat Woreda. However, a detailed knowledge of the hydrogeologi:al development potential of the proposed project area is lacking. Borehole drilling and geophysical survey equipment are available at the Tigray Waterworks Construction Enterprise in Makelle. Therefore, the proposed project area is a good candidate to use as a case study for the KAR programme. Unfortunately, the ongoing political situation between Ethiopia and Eritrea precludes any KAR programme activity in the area at present. The results of this visit have been used to produce summary field aids for use by local staff and others interested in the development of the area. These sheets outline the different types of geological strata present and their associated hydrogeological development potential

Contents

l.

Introduction

1

2.

Background Information on Ethiopia and the Hintalo-Wajerat Woreda Region

4

3.

Groundwater Availability

15

4.

Current Practice - Methods and Approaches

18

5.

Availabk Inronnation ancl Data Colkction

6.

Conclusions

23

7.

Recommendations

24

References

25

Acknowledgements

25

ANNEXA

Introduction to the Project

26

ANNEXB

Itinerary

29

ANNEXC

People Met and Other Contacts

31

ANNEXD

Maps and Reports Collected During Visit

33

ANNEXE

Simplified Groundwater Development map and Summary Table for the Oju/Obi Area, Nigeria

35

Reconnaissance groundwater survey results, Hintalo-Wajerat Woreda, Southern Tigray, Ethiopia

38

ANNEXF

ii

List of Figures

Figure 1

Map of Ethiopia showing location of the study area within Tigray

Figure 2

Map ofTigray Region showing location ofHintalo-Wajerat Woreda

Figure 3

Map of Hintalo-Wajerat Woreda showing tabia boundaries

Figure 4

Summary hydrogeology map of the Hintalo-Wajerat Woreda with major topographic areas (based on Hydrogeology of Mekele (Sheet ND37-ll) Ethiopian Ministry of Mines, Energy and Water Resources (!978). NB Letters and boundaries refer to geological units on Figure 5

Figure 5

Summary geology map of the Hintalo-Wajerat Woreda (based on Geology of Mekele (Sheet ND37-11) Ethiopian Ministry of Mines, Energy and Water Resources (!971).

List of Tables

Table 1

Population and livestock distributions per tabia within Hintalo-Wajerat Woreda

Table 2

Monthly mean, minimum and maximum rainfalls at Makelle and Wukro (mm) for 1992-1997, from EOC (!999)

Table 3

Startigraphic succession found within the Hintalo-Wajerat Woreda area

Table 4

Existing beneficiaries of safe water and list of water sources needed in HintaloWajerat Woreda (from Ethiopian Orthodox Church, 1999)

iii

List of Plates Plate 1

Antalo Limestone at Muja

Plate 2

Agula Shale west of Adi Gudom, with horizontal and dipping gypsum bands developed along bedding planes and joints respectively

Plate 3

Mixed matrix supported conglomerate within the Amba Aradam Sandstone south east of Hi wane

Plate 4

Cliffs of laterized Amba Aradam Sandstone south east of Hi wane within the Adi Shoha Highlands

Plate 5

Broken-off white Amba Aradam Sandstone within black Trap Volcanics basalts

Plate 6

Prominent Makelle Dolerite sill within Antalo Limestone cropping out along valley side west of Mai Nebri

Plate 7

Successive Trap Volcanic Basalt flows with irregular surfaces cropping out near Debub

Plate 8

Columnar jointing within thicker Trap Volcanic Basalt flow between Adi Gudom and Debub

Plate 9

Intermountain fan delta with irrigated terraces south east of Hi wane

Plate 10

Deep gully eroded through black peaty cotton soil into underlying coarse grained alluvium south of Mai Nebri

Plate 11

Local women pumping water from an Afridev equipped shallow borehole east of Adi Gudom

Plate 12

River-side spring from alluvial gravels and boulder beds beneath black cotton Soil at Debub.

Platel3

Disused, apparently contaminated hand dug well at Debub

Plate 14

Borehole equipped with an electrical submersible pump supplying local domestic reticulation scheme at Mai Nebri

Plate 15

Protected spring at Sofa west of Mai Nebri

Plate 16

Cliff top irrigated area fed by spring on dolerite/limestone contact zone at Muja

IV

List of Abbreviations

BGS BPED DFID EBr EOC/DICAC GIS GPS GSE KAR NGO WMERB

British Geological Survey Bureau of Planning & Economic Development Department for International Development Ethiopian Birr Ethiopian Orthodox Church/Development and Inter-Church Aid Commission Geographical Information System Ground Positioning System Geological Survey of Ethiopia Knowledge and Research Non Governmental Organisation Water Mines and Energy Resource Bureau, Make!le

v

Technical glossary

Aquifer- A rock formation that contains sufficient groundwater to be useful for water supply. Aquiclude- A relatively impermeable rock (e.g. shale) that does not transmit water rapidly enough to supply a well or spring. Basalt -Fine-grained, dark, igneous rock. Groundwater flow is primarily through fractured zones. Borehole - A cylindrical hole, usually greater than 20 m deep and I 00 mm in diameter constructed by a drilling rig to allow groundwater to be abstracted from an aquifer. Note: American use of the term 'well' to mean both boreholes and shallow wells. Geophysics - Techniques for measurement of the physical properties of rocks without drilling boreholes. In certain circumstances results from geophysics surveys can be used to infer the presence of groundwater. Karstic - types of features developed in limestone or dolomite areas where water movement has enlarged joints and fractures by dissolving or solution. Karstic features can form important groundwater-bearing horizons. Laterized - the process of creating laterite; the weathering of igneous rocks under tropical conditions to form clays. Mesa- Flat-topped, steep-sided plateau. Palaeosol - a buried soil horizon from the geological past. Porosity -The ratio of void space in rock to the total rock volume - expressed as a percentage. Rocks with high porosity can store greater volumes of groundwater. Permeability - Rate of groundwater flow through a cross section of aquifer. Permeability is higher when there are interconnected fractures. Pumping test- A test that is conducted to determine aquifer or borehole characteristics. Sandstone - A rock that is made from cemented sand grains - usually has a high potential for groundwater. Shallow well - A large diameter (usually greater than I m) hole, dug to less than 20 m depth to access groundwater. Siltstones and mudstones - Fine-grained rocks made of mud and or very fine-grained particles. Usually have a low potential for groundwater. Success rate (borehole drilling) - Imprecise term, normally taken as the number of successful boreholes divided by the total number of boreholes drilled - expressed as a percentage. Different organisations have different measures for denoting a successful borehole. Transgressive/regressive cycle - a rise and subsequent fall in sea-level which affects the types of sediments deposited. Travertine - A variety of pale coloured calcareous tufa, some varieties of which are porous. Characteristic of hot springs in volcanic regions.

vi

Weathered zone- A layer of rock beneath the soil zone that has been altered by physical breakdown or chemical decomposition. Yield- The volume of water discharged from a well or borehole, measured in m 3d. 1 or ls- 1

VII

1.

INTRODUCTION

During March 2000, Water Aid invited a team from the British Geological Survey (BGS) to travel to Ethiopia to assess groundwater development problems faced in the Hintalo-Wajerat Woreda, located in the Southern Zone ofTigray Region, northern Ethiopia (Figures 1 and 2). Within the Woreda area, WaterAid and their partners realise that access to potable surface water sources is limited while groundwater development is constrained by difficult geological conditions. This report details the key findings of the visit, and provides a record of information gathered and people met. This assessment forms part of a two-year project aimed at developing groundwater development tools to increase the success of water supply projects in geologically difficult areas of sub-Saharan Africa. The project is funded by the Department for International Development (DFJD) under the Knowledge and Research (KAR) programme. Groundwater development problems facing four WaterAicl programmes in Ghana, Ethiopia, Tanzania and Zambia are being examined. Techniques developed during the project will be used to produce groundwater development maps for two areas where the siting of sustainable groundwater supplies has proven difficult. A brief introduction to the project is provided in Annex A.

Two BGS staff, Jeffrey Davies (Hydrogeologist) and Philip Men·in (1-IY.drogeologist), visited Ethiopia between 6-l5th March 2000. WaterAid facilitated the visit; an itinerary for the visit is given in Annex B. The terms of reference were as follows: (i)

to assess the problems that Water Aid and their partners face in developing groundwater in the Hintalo-Wajerat Worcda;

(ii)

to ascertain the current expertise, tools and equipment that WaterAid and partners have to site boreholes and wells;

(iii)

to collect and evaluate data and information relevant to groundwater resource development within the Hintalo-Wajerat Woreda, Tigray State, northern Ethiopia;

(iv)

to recommend follow-up work.

The first two aims were addressed by visiting the area and discussing the occurrence of groundwater there with members of the EOC, government institutions, Makelle University and contract drillers; the third aim was addressed by visiting various institutes in Makelle and Addis Ababa (Annex C).

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2.

BACKGROUND INFORMATION ON ETHIOPIA AND THE HINTALO-WAJERAT WOREDA REGION

Ethiopia has made significant socio-economic improvements since the end of the civil war. However, the Southern Zone of Tigray Region in northern Ethiopia is one of the poorest regions in the country and contains a largely subsistence farming population. At the present time, further development is constrained by the continuing border tension between Ethiopia and Eritrea. Much of the background information presented here has been obtained from a project proposal entitled "Hintalo-Wajerat Water Supply, Sanitation and Hygiene Education Project proposal" prepared by the Ethiopian Orthodox Church for submission to WaterAid. This project aims to improve the water supply status of 55,000 people and 22,000 livestock within one of the poorest areas of Ethiopia. Ethiopia is divided into regions, of which Tigray is the most nmthern and contains the project area. Each region is divided into zones. The project area is located in the Southern Zone. Each zone has a number of woredas (administrative regions). The project area is the Hintalo-Wajerat Woreda that is divided into 19 tabias (or kebeles) similar to parishes (Figure 3). These are then further divided into villages, called kushets. The distributions of community and livestock populations within these labia areas during 1992 are listed in Table 1. The average population density within the Woreda is 2 approximately 125 persons per km .

No.

Tabia

Male

Female

Total

Kushets

Area(Ha)

Livestock

1

Hagre Selam

4321

4355

8676

4

8112

7285

2

Senale

4089

4111

8200

4

3380

4306

3

Hareko

4019

4130

8149

3

2474

4381

4

Adi Gudem

3510

4218

7728

4

2196

9229

5

Ara Asegeda

3837

3787

7624

4

3361

6157

6

Hi wane

3704

3869

7573

4

4558

8673

7

Bahir Tsebha

3653

3897

7550

4

2274

6413

8

Metikele

3452

3413

6865

3

3390

7217

9

FikreAlem

3236

3229

6465

4

5891

5862

10

AmdeWoine

3189

3268

6457

4

2045

2337

11

Gonka Seberbera

3236

3130

6366

4

3706

5182

12

Dejen

3086

3144

6230

3

4447

3238

13

Tsehafi

2978

3009

5987

4

9327

7503

14

Muja

2874

2982

5856

4

12352

6535

15

Adi Awona Waza

2830

2929

5759

4

11865

6800

16

Hintalo

2663

2787

5450

3

3365

7613

17

Adi Keyeh

2657

2580

5237

4

2571

9070

18

Adi Mesena

2405

2617

5022

4

2188

3897

19

Mai Nebre

2149

2366

4515

4

3706

5821

61888

63821

125709

72

91208

117469

Total

Table 1

Population and livestock distributions per Tabia within Hintalo-Wajerat Woreda during 1992

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