Identification of groundwater potential recharge zones using GIS-based multi-criteria decision analysis: A case study of semi-arid midlands Manyara fractured aquifer, North-Eastern Tanzania

Abstract

The extraction of groundwater has recently increased due to water scarcity as a result of human activities including agriculture, industrial and domestic use. This has accelerated the need to spatially identify groundwater potential zones for artificial aquifer recharge and extraction through boreholes drilling. The current study is aimed at identifying groundwater potential recharge zones (GPRZ) of semi-arid midlands Manyara fractured aquifer using Geographic Information System (GIS) and Multi-criteria Decision Analysis (MCDA) based on Analytic Hierarchy Process (AHP) technique. The study area solely depends on groundwater for human survival through deep and shallow boreholes water extraction. Eight influencing factors including aquifer lithology, slopes, land use/land cover (LULC), soil types, drainage density, geological lineament density, flow accumulation, and topographic wetness index (TWI) were determined and reclassified on a scale of 1–5 in ArcGIS 10.6 environments. These factors were weighted with the help of AHP and integrated with ArcGIS pro based on the weighted linear combination (WLC) method. The results were scaled into five recharge potential classes; very high, high, moderate, low, and very low recharge potential zones. The results indicates that about 1607 km2 (14.7%) of the study area is under very high potential recharge zones, 3982 km2 (36.43%) falls under high recharge zones, 3120 km2 (28.55%) moderate, 1658 km2 (15.17%) low and 562 km2 (5.14%) under very low recharge zone. To assess the accuracy of the result a total of 66 boreholes collected from the field were used and the Receiver Operator Characteristics (ROC) curve generated. The area under the curve (AUC) was found to be 78% signifying moderate to higher accuracy of the model. The presented results provide an inventory of information for the land, water, environmental policy maker's authorities, and other stakeholders to enhancing groundwater resource management within semi-arid midlands Manyara basement fractured aquifer of the internal drainage basin North-Eastern Tanzania.