Site Suitability Analysis for Different Indigenous Rainwater Harvesting Systems - A Case Study of Sana'a Water Basin
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Nowadays, the management of water resources in Sana’a Water Basin is a complex issue due to limited data, rapid population growth, aridity and complex physiographic environment. Groundwater is the main water resource in the basin for domestic, agricultural and industrial uses, in which the agricultural sector consumes about 90% of this resource. As a result, the groundwater level is declining rapidly. Rainwater harvesting systems (RWH) are a prominent solution to deal with water scarcity by conserving available water resources and the energy needed to deliver water to the water supply systems. The impact of climate change on water resources can also be reduced by rainwater harvesting. Accordingly, RWH is becoming an important part of the sustainable water management around the world. The identification of suitable sites for RWH is an important step to maximize the water availability, land productivity, and groundwater conservation in arid and semi-arid areas. This study aims to select the optimum sites for different indigenous RWH systems in Sana’a water basin through the use of modern techniques such as Geographic Information Systems (GIS), Remote Sensing (RS) and Multi-criteria Analysis (MCA). The selection criteria in this study is based on five biophysical factors as well as six socio-economic parameters. These criteria were identified based on intensive literature review. Five local experts are asked to evaluate and determine the relative importance of each criterion to each other. Then, the consistency ratio between the experts’ opinions was evaluated using the pairwise comparison method and a final weight was computed for each criterion. In addition, the local experts were asked about their views on the proper locations within Sana’a basin for each RWH system and this information is used to validate the results of the final suitability maps. Based on the literature review, discussions with supervisors and the questionnaire results, four RWH systems are selected in this study, namely, Terraces, Check-dams, Ponds, and Spate Irrigation. Therefore, each RWH system is analysed individually and has its own suitability map. The Weighted Linear Combination (WLC) technique was applied in combination of the Boolean technique to generate the final suitability maps for RWH systems in Sana’a basin. The results of the suitability maps indicated that a sufficient area of high and very high suitability are existed in the study area for the four RWH systems, particularly terraces, check dams, ponds, and spate irrigation, which are 33%, 35%, 33%, and 32% respectively. Accordingly, Sana’a water basin is in general well suited for the implementation of RWH systems.