Site suitability mapping of earth dams in Uganda’s cattle corridor: A case study of Nakasongola district
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In Uganda, water scarcity is a major challenge faced by livestock farmers. Over the last 10 years, climate change has further worsened the situation and jeopardized livestock owners’ livelihoods (Barihaihi, 2010). Uganda’s cattle corridors are generally too dry for crop production with an annual rainfall of 500-1000mm and suffer from land degradation caused by overgrazing and increasing harvesting of trees for charcoal burning (FAO, 2011). Although the government and other development partners have made considerable efforts to avail water to these communities through earth dam construction, there was a huge information gap in the distribution patterns and accessibility to these earth dams by livestock farmers. Little was also known of the criteria followed or being followed to select suitable sites for constructing earth dams in these areas. The study focused on assessing characteristics of existing earth dams, development of GIS-based suitable sites of dams, and evaluated spatial accessibility to these dams. Primary data for this study was collected through a questionnaire survey, interviews and utilization of a hand-held GPS receiver to capture the location of dams. Spatial distribution assessment of Earth dams was carried out using the nearest neighbor tool in ArcGIS 10.6. To model potential sites of earth dams, soil, rainfall, DEM, land cover datasets were processed and overlaid using ArcGIS weighted overlay tool. Also, ArcGIS buffer tool was used to assess accessibility distances to earth dams by communities. Results showed that more people in area used dams as a source of water for their livestock especially cattle, and majority of the dams (59%) had a capacity of 3000m3 of water constructed in 2013 by the government. In terms of spatial distribution of existing dam, Migera town council had many dams concentrated in the area and less in other sub counties. Based on GIS modeled suitable sites, about 30 sites were found to be suitable for locating dams representing 10.9% of the total area, and most of them were clustered. For spatial accessibility, majority of Households (50%) would have to travel 10kms to the dam sites and least (10%) would have to travel 30kms to access the dams. 5km radius was to be travelled by 25% of households. The study showed that there was unequal distribution accessibility of residents to existing earth dams. Also, GIS-based approach as a spatial analyst tool coupled with the use of spatial datasets (factors) to determine earth dam sites, proved to increase the level of accuracy for determining areas for locating suitable dam sites that is well distributed minimizing biasness. For further studies, high-resolution sources of all related datasets are recommended to improve the accuracy. Management committees should be formed and they should be given specialized training in managing and maintaining earth dams.