Water harvesting in Erbil Governorate, Kurdistan region, Iraq : detection of suitable sites using geographic information system and remote sensing

Abstract

The drought effects on Iraq, and specifically on the Kurdistan region, is on the rise due to the climate change. Management of the water resources has become necessary to solve this problem. The aim of this study is to identify suitable zones for rainwater harvesting in Erbil governorate, Iraqi Kurdistan Region, by using Geographic Information System (GIS) and Multi Criteria Evaluation (MCE) as a tool for decision support. Multi criteria evaluation is carried out in Geographic Information System to help the decision makers in determining suitable zones for rainwater harvesting. The criteria which were taken into account for multi criteria evaluation are; soil texture, slope, rainfall data (2000-2011), land use/cover and drainage network. The soil conservation service model was used to estimate the runoff depth. Land use/cover was extracted from LANDSAT satellite imagery (2006) by using remote sensing technique (Idrisi software). An analytic hierarchy process (AHP) method was used to estimate the weight for each criterion. The weighted linear combination method was used to incorporate the criteria weight in the multi criteria evaluation operation. The multi criteria evaluation is supporting determination of suitable areas for rainwater harvesting, and suitable zones to construct small and medium dam sites. The total suitable area for water harvesting is 36% of the study area, where 14% represents moderate suitability while 33% indicate very low suitability. Macro catchment is significant in the selection of suitable areas for rainwater harvesting. A contour line map and the drainage network, represented as a Triangulare Irregular Network (TIN), were used to suggest six sites for small and intermediate dams. The total water capacity of these dams is about 165 million cubic meters.Popular science: Find a suitable area for rainwater harvesting Rainwater harvesting is a technique to capture and store rainfall where it falls. The technique of water harvesting can be used for different purposes, e.g providing irrigation water, drinking water, increase groundwater recharge, and reduce flood risk. The application of rainwater harvesting is suitable in arid and semi-arid areas, where the amount of the water (rainwater as well as available water in strems, wells etc.) changes from year to year. Erbil governorate in Iraqi Kurdistan Region needs to find suitable zones for rainwater harvesting to be used for different purposes, mainly because of irregular rainfall and drought. Geographic Information System have suitable tools to help the decision makers in identifying suitable areas for water harvesting. There are different factors that are used to determine suitable areas, including rainfall data, slope map, soil information, drainage map and land cover/use map. Each factor has a certain importance/weight, which depends on the importance of this factor in determining suitable zones for rainwater harvesting. In this study a multi-criteria evaluation method was used to estimate the weight of each factor, and to combine these factors in order to find suitable areas for water harvesting. The result shows that the total suitable area for water harvesting is 36% of the whole study area, mainly located in the northern parts of Erbil governorate. This means that it will be relatively easy to select suitable sites for water reservoirs, in this study exemplified by small and medium dams, in this part of the study area