Groundwater recharge estimation and potential recharge mapping in the Afram Plains of Ghana using SWAT and remote sensing techniques

The Afram Plains watershed is one of the major watersheds located at the lower part of the Volta Basin in Ghana with high groundwater usage. Dependency on groundwater is a fast-growing concern in the plains due to the unreliable supply of surface water. This has put the groundwater resources under intense pressure and has necessitated the need for sustainable management of the groundwater resources. This study aimed to estimate the recharge, spatial distribution, and potential recharge zones of groundwater at different scales in the Afram Plains area using the Soil and Water Assessment Tool (SWAT) model and Geography Information System (GIS) approach. The SWAT model was set up (1983-2016), calibrated (1983-1990) and validated (1991-1997) using digital elevation model, soil, land use, climate datasets, and discharge data. The GIS approach was used to produce thematic maps for eight contributing factors; rainfall, elevation, land cover land use, lineaments, drainage, geology, soil and slope for mapping the recharge zones. The results showed that about 1.65% (19.3 mm) of the SWAT simulated mean annual rainfall (1176.9 mm) is converted into groundwater recharge in the watershed. The potential recharge zones categorized as very poor, poor, moderate and high zones have area coverages of 0.58% (20.8 km(2)), 22.4% (798 km(2)), 60.9% (2169 km(2)), and 16.2% (576 km(2)), respectively. The potential recharge zones after validation over boreholes and wells data indicated that the Afram Plains area is dominated by the moderate potential zone.