GIS-AHP based delineation of groundwater potential zones in the Lake Hawassa watershed, Ethiopia

Groundwater is the most widely distributed natural resource that serve as a major water source for drinking, industrial use, and irrigated agriculture. Globally several regions are facing challenges related to water scarcity. On the other hand, groundwater exploration technologies such as geophysical investigations are expensive particularly for developing regions. In this study, we aim to delineate and assess the groundwater potential zones of Lake Hawassa watershed (LHW) in Ethiopia using GIS-AHP based techniques. Eight major factors that influence the occurrence and movement of groundwater i.e. geology, geomorphology, rainfall, soil, lineament density, slope, land use/land cover and drainage density were used in the delineation and assessment of groundwater potential zones. The pair-wise comparison matrix and weighted overlay analysis were applied to compute the factor score weights. Accordingly, Groundwater Potential Index unit scale values were classified into five groundwater potential zones i.e. very low, low, moderate, high, and very high. The finding showed that, geology is the most influential factor for groundwater occurrence. In most central part, i.e. the floor of the watershed was delineated as high to very high groundwater potential zones. More than half of the study regions (51.18%) constitutes moderate groundwater potential zones. On the other hand, low and very low potential zone, 8.09% and 0.53% respectively is present in areas which mainly constitute relief hills and summit areas. The validation result showed that 92.5% of high productive wells coincide with high groundwater potential zones of LHW; which suggest, GIS-AHP based techniques were good tools to delineate groundwater potential zones. The results will help in systematic and proper development and management of groundwater resources in the LHW.