Investigation of Suitable Sites for Rainwater Harvesting Planning using Geographic Information System and Remote Sensing Techniques in the Western Desert of Iraq

Abstract

The Western Desert is considered as one of the biggest arid regions in Iraq suffering from severe water shortage, mainly due to its climatic conditions and lack of water resources planning and management. Water storage could alleviate the impacts of drought, this may be accomplished by building dams and ensuring water supply. Detecting suitable sites for rainwater harvesting (RWH) to support planning and management of water resources is a complex issue and can be time consuming. The new information technologies, such as Geographic Information System (GIS) and Remote Sensing (RS) data have assisted and simplified the process of site selection for RWH and planning. This study has three objectives: (1) to create digital soil map using Artificial Neural Network (ANN) model integrated with GIS, RS and survey data; (2) to estimate surface runoff for Hijlan, Fahami and Zgadan valleys using the incorporation of the Soil Conservation Service Curve Number (SCS-CN) approach with the GIS; and (3) to detect proper RWH sites by integrating RS and GIS with a multi-criteria decision technique. The results demonstrate that the Radial Basis Network (RBNN) model has proven to be successful in predicting the spatial distribution of clay soil, followed by both silt and sand. It has also been noted that the Root Mean Square Error (RMSE) for clay, silt and sand was 4.2 %, 9.5 % and 11.0 %, respectively. Moreover, spectral reflectance and clay soil were highly related with coefficient of correlation value of (0.749). Furthermore, of the twenty-five samples defined by the USGS, only four samples had minor variations between the estimated and measured soil texture category. The results of the incorporation of the SCS-CN with GIS revealed that the runoff depth ranged from 12.5 mm to 20.3 mm for (48mm) for the maximum storm of rainfall recorded at Haditha station through 2018, while the amount of runoff of the maximum storm were 7,388,700 𝑚3 , 12,750,000 𝑚3 and 9,851,590 𝑚3 for Hijlan, Fahami and Zgadan, respectively. Seven criteria were used in the site selection process: Runoff, slope, soil texture, land use land cover (LU), distance from irrigated lands, distance from residential areas, and distance from roads. The stream order and distance from faults were used in the Boolean overlay method. The results indicated that the final map can be divided into vii three categories of suitability: (i) Highly suitable with 6% coverage (117 k𝑚2 ), (ii) Moderately suitable with 4% coverage (78 k𝑚2 ), and (iii) Least suitable with 90% coverage (1758 k𝑚2 ) of the basin area. It is indicated that only one earth dam could be executed for every valley. This low data-intensive and cost-effective methodology offered can be adopted in arid regions to embrace RWH as an efficient strategy to handle growing water scarcity