Geospatial Technique Integrated with MCDM Models for Selecting Potential Sites for Harvesting Rainwater in the Semi-arid Region

Abstract

Severe droughts and mismanagement of water resources during the last decades have propelled authorities in the Kurdistan Region to be concerned about better management of precipitation which is considered the primary source of recharging surface and groundwater in the area of interest. The drought cycles in the last decades have stimulated water stakeholders to drill more wells and store uncontrolled runoff in suitable structures during rainy times to fulfill the increased water demands. The optimum sites for rainwater harvesting sites in the Qaradaqh basin, which is considered a water-scarce area, were determined using the analytical hierarchy process (AHP), sum average weighted method (SAWM), and fuzzy-based index (FBI) techniques. The essential thematic layers within the natural and artificial factors were rated, weighted, and integrated via GIS and multi-criteria decision-making (MCDM) approaches. As a consequence of the model results, three farm ponds and four small dams were proposed as future prospective sites for implementing rainwater harvesting structures. The current work shows that the unsuitable ratio over the study area in all methods AHP, SAWM, and FBI occupied 12.6%, 12.7%, and 14.2% respectively. The area under the curve (AUC) and receiver operating characteristics were used to validate the model outcomes. The AUC values range from 0.5 to 1, meaning that all MCDM results are good or are correctly selected. Based on the prediction rate curve for the suitability index map, the prediction accuracy was 72%, 57%, and 59% for AHP, SAWM, and fuzzy overlay, respectively. The final map shows that the potential sites for rainwater harvesting or suitable sites are clustered mainly in the northern and around the basin’s boundary, while unsuitable areas cover northeastern and some scatter zones in the middle due to restrictions of geology, distance to stream with the villages, and slope criteria. The total harvested runoff was 377,260 m3 from all the suggested structures. The proposed sites may provide a scientific and reasonable basis for utilizing this natural resource and minimize the impacts of future drought cycles.

An integrated new approach for optimizing rainwater harvesting system with dams site selection in the Dewana Watershed, Kurdistan Region, Iraq

“…Criteria restriction is an important aspect to consider when creating water harvesting techniques [ 9 , 19 , 20 ]. GIS spatial analysis tools create special geographical features by using buffer zones around criteria [ 26 ].…”

“…GIS spatial analysis tools create special geographical features by using buffer zones around criteria [ 26 ]. Each criterion for selecting a dam site should be described by the distance recommended by experts, taking into account environmental concerns and extra costs, and complying with relevant government rules [ 9 , 19 ], as shown in Table S2 .…”

“…Soil texture greatly impacts the selection of a suitable RWH site by influencing infiltration rates and runoff volume [ 33 , 46 , 47 ]. To identify soil texture in the study area, 21 soil samples were collected from different locations except for mountain areas, which are classified as thin or absent soil cover and have high infiltration rates [ 9 ]. The samples were analyzed using the pipette method, and soil texture classes were created based on the United States Department of Agriculture (USDA) triangle classification, as shown in Fig.…”

“…The Dewana watershed area, which is one of the agricultural and tourism hotspots, is confronting a water shortage. It obtains its water primarily from springs, ephemeral streams, and groundwater, such as wells, for irrigation and household needs [ 9 ]. The authorities in the IKR are focused on enhancing the management of precipitation, recognized as the primary source of surface and groundwater replenishment in the region.…”

“…[ 19 , 20 ] concentrated on identifying optimal dam sites in the Greater Zab and Khabour River basin. However, only [ 9 ] has been conducted to develop a comprehensive and integrated GIS-MCDA approach for selecting suitable dam sites in the area. The existing literature lacks a holistic approach that considers the synergy between RWH and dams to maximize water availability and sustainability in the Dewana Watershed.…”