Assessment of suitable sub-watersheds for sand dams and prioritization of artificial sandy aquifers for sustainable groundwater development

This study was conducted in the Motloutse Basin in eastern Botswana, with the aim of assessing the suitability of the sub-watersheds for the deployment of sand dams and prioritising them for the formation of artificial sandy aquifers. Morphometric and geological analyses were conducted using the base map with the Spatial Analyst tool of ArcGIS Pro 3.4 software. The Motloutse Basin is made up of ten sub-watersheds (SWs), namely SW 1 to SW 10, defined based on elevation, slope and drainage flow direction. On the basis of suitability for sand dam construction, morphometric analyses ranked the sub-watersheds from SW1 to SW9, and geological coverage analyses ranked them from SW1 to SW3. The integrated analyses of sub-watershed geological cover and morphometric rankings indicate that SW 7 is the most suitable sub-watershed, followed by SW 2, SW 3, SW 4, SW 6, SW 8 and SW 9 for sand dam construction and ultimately formation of artificial sandy unconfined aquifers. All seven sub-watersheds offer multiple feasible sites for the sand dam construction and the formation of artificial sandy unconfined aquifers to enhance groundwater availability in the basin. For the remaining three sub-watersheds (SW 1, SW 5 and SW 10), the sand behind the dam structure can effectively serve as a recharge medium to the underlying highly porous and permeable geological formations. The three sub-watersheds are recommended for groundwater recharge that promotes percolation into the local groundwater system. The findings in this study assist with the implementation of groundwater resource management practices that enhance groundwater availability and improve the overall ecosystem status of the basin.