INTEGRATION OF GEOGRAPHICAL INFORMATION SYSTEMS AND MULTI-CRITERIA DECISION ANALYSIS TO DETERMINE SUITABLE LOCATIONS FOR RAINWATER HARVESTING IN ERBIL PROVINCE, IRAQ

Abstract

Over the past two decades, climate change has severely impacted Erbil province in Iraq, leading to significant droughts that have caused water shortages and extensive damage to the agricultural lands, particularly in the southern portions. In response to this adverse climatic phenomenon, the present study proposes rainwater harvesting (RWH) as a drought adaptation strategy and an alternative water source for agricultural irrigation in the region. To implement this approach, the study identified the most suitable locations and types of RWH structures within the area using geographic information systems (GIS)-based multi-criteria decision analysis (MCDA). Initially, an RWH suitability map was generated, categorizing the study area into different RWH suitability levels based on various factors, including climate, hydrology, topography, agronomy, and soils. Seven criteria were selected and prepared as thematic layers: rainfall, runoff, land use/cover (LU/LC), soil texture, slope, drainage density (DD), and topographic wetness index (TWI). Expert judgments were used to assign weights and rank criteria, and the consistency of these judgments was evaluated using the analytical hierarchy process (AHP) method. The weighted criteria were then combined to generate the RWH suitability map, revealing four suitability classes: very highly suitable, highly suitable, moderately suitable, and less suitable. These classes cover areas of 1583.25 km² (10.67%), 4968.55 km² (33.49%), 5295.65 km² (35.69%), and 2989.66 km² (20.15%), respectively. The results highlight the northern and central regions as particularly suitable for constructing large and medium RWH structures, while the southern portions are ideal for smaller structures. Subsequently, the study identified several optimal sites for different RWH structures. For this purpose, a basin map of the study area was generated and compared with the LU/LC map to identify basins containing or near agricultural land. These selected basins were then analyzed based on topographical, hydrological, and socio-economic characteristics to determine the specific suitable locations and types of RWH reservoirs. The study identified one ideal site for a mediumdam, named Bastora Dam, with a storage capacity of 84.5 million m³ of water. Additionally, three ideal locations for check dams were identified: TaqTaq, Hamamok, and Debaja, with storage capacities of 7.4, 28.8, and 37 million m³, respectively. These reservoirs were named after the nearby villages. Moreover, the study identified 31 suitable sites for farm pond construction. These RWH reservoirs can significantly assist farmers in these regions by providing sufficient water for supplementary irrigation. The findings of this study offer valuable insights for water resource planners and managers, supporting strategic planning and effective water resource management in the study area and providing potential solutions to the pressing challenges of water scarcity