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MANAGEMENT PRACTICES USING OF AGRICULTURAL DRAINAGE WATER WITH DRIP IRRIGATION FOR CROP PRODUCTION AND LANDS SUSTAINABILITY IN ARID AND SEMI-ARID AREAS Ali Heydar Nasrollahi1,*, Saeed Boroomand Nasab2, Abdol Rahim Hooshmand3

Abstract In addition to lack of water, other elements such as high temperature, severe salinity of soil and water quality create problems in arid and semi-arid areas. Nowadays restricted water resources having acceptable quality has resulted into the reuse of low quality water such as agricultural drainage water in these areas. The use of drainage water and saline water in agriculture requires different management practices on the farm, such as increasing the efficiency of water use, leaching and soil desalinization, in addition to proper drainage and other conventional methods. High efficiency Irrigation methods with such as drip irrigation are suitable solutions for the optimal use of these resources. This study was carried out to investigate the effects of drip irrigation management strategies using saline water on corn crop in the research farm of the Water Science Engineering faculty at Ahwaz, Shahid Chamran University. The experiment was performed on split plots based on a randomized complete block design. In this research the effects of three irrigation management options; that is mixing (M1), one-alternate mixing (M2) and half-alternate mixing(M3) of three levels of saline water (S2, S3 and S4) with the Karun river water (S1), and the reviewing of its effects on yield, irrigation water productivity of corn and soil salinity was investigated. Irrigation management strategies and salinity were the main factor and sub-factors. Salinity levels of S2, S3, and S4 were 4, 6 and 8 dS/m respectively. Results showed that the effects of management and salinity and their interaction on yield and water productivity were significant at levels of 5 percent. The application of the half-alternate (M3) method improved yield indexes, water productivity and the leaching of soil surface layers. The Model coefficients of yield- salinity were calculated under different management scenarios of drip irrigation. The yield reduction per unit increase in soil salinity in the plant root zone the mixing, one-alternate and half-alternate management strategies were calculated respectively as being at 9.86, 12.3 and 7.14 percent. The results of this research show that drip irrigation when applied with proper management is a safe method to reuse large amounts of drainages water volumes in arid and semi-arid regions.

1

Assistant Professor, Department of Water Engineering ,Faculty of Agriculture and Natural Resources, Lorestan University, Iran. *Corresponding author: [email protected], [email protected] 2 Professor of Irrigation Department, Shahid Chamran University of Ahvaz, Iran 3 Associate Professor of Irrigation Department, Shahid Chamran University of Ahvaz, Iran. 607

KEY WORDS: Water quality, Drainage water, Water reuse, Drip irrigation.

Introduction In addition to the shortage of water, high temperature, severe salinity of the soil create problems in arid and semi-arid areas. Nowadays, drip irrigation can overcome particularly any environmental limitations for sustainable crop production. The Increasing water use efficiency in modern irrigation systems and the use of unconventional water resources such as saline and brackish water are the most effective strategies for optimal use of water resources in agriculture. In this regards, nowadays drip irrigation using saline water has been considered for various crops in many parts of the world (Wan et al., 2012; Wan et al., 2013). The studies show that drip irrigation can distribute water uniformly, and control the amount of water used precisely, moreover it aids in increasing plant yields, reducing evapotranspiration and percolation, and decreasing the dangers of soil degradation and salinity (Karlberg and Frits, 2004). Growth retardation is the most important response of plants to soil salinity. With an increasing solute concentration to more than the root threshold of the plant, the growth rate and plant size declines. Irrigation methods can affect the plant response to salinity. Drip irrigation, with its characteristic low rate of water usage and highly frequent irrigation applications over a long period of time, can retrain a high soil matric potential in the root zone thus compensating the decrease of osmotic potential introduced by the saline water irrigation regimen, and the constant high total water potential that is maintained for crop growth. At the same time, well-aerated conditions can be maintained under drip irrigation. Hanson et al. (2010), stated that the only way to solve the problem of soil salinity and drainage in California is the improving of irrigation methods such as the use of drip irrigation. Kang et al. (2010), studied the effects of drip irrigation with saline water on maize yield. Results indicate that irrigation water with a salinity 2,0 m above sea level), leaching of salts hasn`t been and won`t be successful. The salt level in the soils remains although leaching was done. Because of existing heavy soils (clay and silty loams) in the Khuzestan plain, the capillary uprise can be estimated to be at least around 50 - 70 cm. Within current subsurface drainage systems, capillary dynamics that are dominating after irrigation stop lead to a re-salination of soil resources. Deep drains lead to additional saline drainage water quantity and salinity. These processes are illustrated in Figures 3 and 4.

Figure 1: Map of surface level above sea level (Khuzestan Province) Data Source: KWPA

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Figure 2: Furrow irrigation and leaching (wheat crops) on saline soil, no groundwater, no subsurface drainage

Figure 3: Furrow irrigation and leaching (wheat crops) and subsurface drainage on saline soil with saline groundwater

Figure 4: Salinization after furrow irrigation (wheat crops) and subsurface drainage on saline soil with saline groundwater 642

Proposed drainage water management solutions Establishing a broader context that facilitates the design of an IWRM approach which positively affects Khuzestan´s natural resources and in turn its society should be a main concern in current strategic planning. As there is an urgent need to overcome drainage water mismanagement circumstances, especially in some southern and western areas, several effective short-term solutions are needed. However, as the overall achievement should be to design and implement a sustainable Integrated Drainage and Wastewater Management System, long-term solutions are equally as important. Reviewing factors responsible for high volumes of saline ADW in Khuzestan draws a multi-layered picture: Factors leading to high volumes of saline drainage water in Khuzestan: - predominance of evaporation over rainfall in non-irrigated lands and anthropogenic influences - heaviness of soil texture and improper soil drainage conditions (insufficient natural drainage) - over-drainage (due to over-irrigation, low water use efficiencies) - improper drain depths and a lack of suitable outlets (Akram et al. 2013) - additional groundwater pumping: drain water salinity is highly affected by groundwater salinity due to deep drainage (Pazira and Homaee 2010) Related management strategies should therefore aim on both the quality and quantity of irrigation and drainage water. Embodying monitoring and control devices, ADW re-use strategies as well as water treatment, namely desalination, are seen as key approaches.

Reduction of the amount of irrigation and leaching water (long term solution) Due to Khuzestan´s semi-arid and arid climate the need to irrigate lands for successful agriculture exists. Whereas precipitation during June-September (Khordad-Shahrivar) is very low e.g. between 0.1 mm to 0.5 mm in Dezful and Hamidiyeh, the evaporation is much higher, e.g. between 322.12 mm to 449.82 mm in Dezful and Hamidiyeh leading to negative water balances. However, from December-March (Azar-Esfand) the precipitation is high e.g. between 25.22 mm to 72.22 mm in Dezful and Hamidiyeh. Contrary, the evaporation is much lower, e.g. between 53.74 mm to 99.11 mm in Dezful and Hamidiyeh. Figure 6 indicates that the annual climatic water balance varies significantly within Khuzestan. Based on these conditions, it is assumed that agricultural drainage water management problems mostly exist during the winter period December-March (AzarEsfand).

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Figure 5 Monthly average rainfall in selected meteorological stations in Khuzestan Data Source: DCE (2009)

Figure 6: Climatic water balance (annual) Khuzestan Data Source: KWPA

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The annual over-use of water for irrigation is a major problem in Khuzestan. Hence, increasing water use efficiencies automatically leads to a reduction of the amount of the water that enters the drainage network and hence to less drainage water volumes. Big gaps exist between water delivery from main canals and water application in the field. The emphasis has been much more on the developmental side of water resources instead of sustainably managing existing water resources. High rates of groundwater extraction worsen the situation and due to annual overdrafts, groundwater tables are declining in many areas (Ul Hassan 2007). One main challenge is to improve the efficiency within existing irrigation techniques: In most parts of Khuzestan, farmers are mainly using traditional irrigation techniques such as furrow irrigation, basin irrigation and border irrigation schemes. There are very few instances of pressurised irrigation systems on large area farms. The comparison between irrigation efficiencies of different systems (surface vs. pressurised systems) shows a big difference in the suitability of the respective method. Table 1 shows selected irrigation and drainage networks located in the Karun-Dez River basin. In some networks pressurised systems have already been installed (at least partly), whereas in others surface irrigation is the prevailing irrigation technique. Comparing the lowest overall efficiency (Gotvand, 40%) and the highest (Balarood, up to 68%) reveals that pressurised irrigation systems like sprinkler and drip irrigation, can be a better irrigation method, if properly managed. Due to higher water use efficiencies, pressurised irrigation methods like sprinkler and drip irrigation can increase the surface area under cultivation with the same amount of water compared to traditional surface irrigation techniques. Planning should not only consider new investments into irrigation technology but to optimally equip the respective areas based on local circumstances such as geological conditions and financial budgets. While pressurised approaches can be more effective for irrigation, leaching of saline soils is a prerequisite in some areas. Depending on local conditions, leaching requires surface irrigation methods. Hence, for some cases, a combination of pressurised and surface irrigation methods will be a valuable approach in order to increase yields while saving water. If the transition of surface irrigation towards pressurised systems is not possible to realise, it is suggested for water resource management to focus on the improvement of the existing system. If these systems are designed well and practiced properly by the farmers, they could still achieve reasonable irrigation efficiencies and fair distribution uniformities in the field without using huge amounts of energy and high costs that are associated with the use of pressurised systems (Heydari 2015).

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Table 1: Efficiencies and types of irrigation and drainage in selected networks (Karun Dez basin) Irrigation and Drainage Networks

Efficiency (%)

Irrigation System

Gargar

65

Mianbandan Shushtar

50

Dez

54

Surface, furrow, basin and border

Gotvand

40

Border, Basin, Furrow, Sprinkler

Balarood

64-68

sprinkler-drip- border - furrow and basin

Drainage System

Overall covered canal + storage basin + pump st. (sprinkler irrigation) covered canals + pipes (sprinkler, drip, centre pivot)

surface and subsurface Surface, sub-surface, concrete canal

surface; gravity

Data Source: KWPA

Note: If increasing irrigation efficiency equals an expansion of agricultural areas (more fields, higher yields) which requires more additional inputs such as fertilizer and pesticides, the impacts on water quality due to changes in the intensity of cultivation must be considered.

Establishing irrigation control systems Establishing irrigation control systems based on modern technology to increase water use efficiency will be another step towards reducing the amount of ADW. The incorporation and adaption of historical and future climatic data as well as respective crop water demands is, beside water-saving irrigation technologies, of highest importance towards an increased water use efficiency. The fact that drainage water discharge lead to an overflow of evaporation ponds and wetlands in Khuzestan means, that the amount of irrigation applied is mostly higher than PET rates. The overcalculation of irrigation water within all irrigation networks of Khuzestan can be seen as one major mechanism leading to the high amounts of drainage water. In order to establish effective irrigation control systems, weekly evaporation rates of respective reservoirs have to be the base for calculations of the required amount. PET rates (mm) accumulated in million m3 are a basic threshold for irrigation water supplied throughout the year (Tables 2-3). By making use of these factors, respective threshold capacities of drainage discharge structures (e.g. evaporation ponds, wetlands) can be estimated as shown in Tables 4-5. The two examples, Korramshar and Hur ol Azim, can be seen as “hotspots” in terms of ADW mismanagement. Respective drainage water structures as well as their locations are presented in Figure 5. 646

As climatic data as well as irrigational practices change throughout the course of the year, automated, flexible control technologies, based on weekly or even daily values are needed. As further important input data like salinity of soils and groundwater as well as crop specific water demands do not exist in areas of interest, the scope of research and data collection has to be extended in order to establish adaptive irrigation control systems. By the controlled provisioning of additional water not only the expected improvement of water use efficiencies but also higher yield performance, yield security and product quality can be achieved. This considerably contributes to environmental protection as it leads to controlled nutrient cycling in the soil with optimum soil moisture content and decreased nutrient leaching. For a field-related optimum control of irrigation, information about the course of the weather, soil type, plant stock and irrigation technologies and techniques applied are needed. An example of a commercial irrigation control system presents IRRIGAMA. It can be described as an internet-based modular built expert and management system that is comprehensible and manageable in practice in field-related conventional and integrated agriculture. Beside quantity control, the establishment of an additional quality monitoring system for irrigation is essential. As irrigation water is almost exclusively taken from surface water bodies without prior treatment, the existing hydrometrical monitoring stations, established and supervised by KWPA, are currently the main institutions for quality control. Additionally, Web GIS, a web-based data portal that delivers basic functionalities on GIS base, would be a valuable extension. GIS in general can deliver huge possibilities and offers an almost infinite amount of tools and functionalities. By incorporating Web GIS, the actual status of the existing water management system could be greatly transformed towards more accuracy and flexibility.

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Table 2: Monthly evaporation rate (in Mio. m3) in the reservoirs Khoramshahr (2005-2014)

Table 3: Monthly evaporation rate (in Mio. m3) in the reservoirs Hur ol Azim wetlands (2005-2014)

Month

Station Bozi Shadegan

Reservoir 1 114 km2

Reservoir 2 145 km2

Reservoir 3 66 km2

Reservoir 4 54 km2

Month

Station Hamidiyeh

Reservoir1 84 km2

October November December January February March April May June July August September sum

300,71 161,71 92,94 70,82 78,79 126,04 174,43 318,65 442,75 497,98 490,89 428,89 3184,60

34,28 18,43 10,59 8,07 8,98 14,36 19,88 36,33 50,47 56,76 55,96 48,89 363,00

43,60 23,45 13,48 10,27 11,42 28,27 25,29 46,20 64,20 72,21 71,18 62,19 461,67

19,85 10,67 6,13 4,67 5,21 8,32 11,51 21,03 29,22 32,87 32,40 28,30 210,18

16,28 8,73 5,02 3,82 4,25 6,81 9,41 17,20 23,91 26,87 26,51 23,16 171,97

October November December January February March April May June July August September sum

226,25 139,72 63,37 46,78 68,24 116,47 200,45 286,02 399,45 442,62 416,18 347,02 2753,45

19,00 11,74 5,32 3,93 5,73 9,78 16,84 24,03 33,55 37,18 34,96 29,15 231,29

Reservoir 2 293 km2 66,29 40,94 18,57 13,71 19,99 34,12 58,73 83,80 117,04 129,69 121,94 101,17 806,67

Reservoir 3 147 km2 33,26 20,54 9,32 6,87 10,03 17,12 29,47 42,04 58,72 65,06 61,17 51,01 404,75

Reservoir 4 304 km2 68,78 42,47 19,26 14,22 20,74 35,41 68,15 86,95 121,43 134,56 126,52 105,49 837,05

Reservoir 5 182 km2 41,18 25,42 11,53 8,51 12,41 21,20 36,48 52,05 72,70 80,56 75,74 63,15 501,13

Data Source: KWPA

Data Source: KWPA

Table 4: Capacity in mio m³ for the reservoirs ‘Khoramshahr’ at 1m and 2m depth

Table 5: Capacity in mio m³ for the reservoirs ‘Hur ol Azim wetlands’ at 1m and 2m depth

depth

Reservoir 1 (114 km2)

1m 2m

114mio m³ 228mio m³

Reservoir 2 (145 km2) 145mio m³ 290mio m³



Calculations: HU Berlin

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depth

Reservoir 1 (84 km2)

1m 2m

84mio m³ 168mio m³





Figure 5: Hur ol Azim and Korramshahr drainage water structures (Data Source: Bing Maps 2016) 649

Redesign of drainage systems in areas affected by shallow and saline groundwater (long term solution) In many low-lying parts of Khuzestan, the amount of drainage water is higher than the amount of irrigation water plus leaching rate because of pumping of additional groundwater into the main drains. Within these areas, it is important to separate the highly saline deep drainage effluent from the leaching and irrigation drainage water. This would positively influence resulting drainage management and reuse strategies in the long run. In order to solve the problem of saline soils in combination with shallow saline groundwater (