ASSESSMENT OF GROUNDWATER POTENTIAL AND QUALITY FOR URBAN AND PERI-URBAN IRRIGATED AGRICULTURE IN THE WA MUNICIPALITY OF GHANA

Abstract

Groundwater resources have been heavily dependent on for domestic and agricultural purposes since the beginning of time. This study was therefore aimed to evaluate the significance of physical and environment factors on groundwater potential, delineate the groundwater potential zones and determine the water quality in the Wa Municipality of Ghana for irrigated agriculture. Nine (9) layers namely; Geology, lineament density, rainfall, drainage density, soil, landuse and landcover (LULC), topographic wetness index (TWI), slope and elevation were considered for modelling the groundwater potential. Weight was assigned to the layers in order of their importance to groundwater occurrence using the analytic hierarchy process (AHP) at a consistency ratio (0.088) which signifies a very high level of acceptance. Geology (19.9 %) was ranked the highest followed by lineament density (18.9 %), rainfall (12.8 %), drainage density (10.6 %), soil (10.1 %), LULC (9.9%), TWI (8.0 %), slope (5.8%) and elevation (3.9 %). The layers were then integrated using ArcMap to map the groundwater potential zones into four (4) classes of low (145.71 km2), moderate (130.15 km2), high (112.39 km2), and very high (185.33 km2). The delineated groundwater potential zones were validated using 40 tube wells data for the study area. The prediction accuracy (AUC) of 0.703 was obtained. The study revealed that about 448.43 km2 land area of the Wa Municipality representing 77.41% of the total area of the municipality has suitable groundwater for irrigation. However, it was discovered that the remaining 22.59 % of the total municipality have concentrations of ammonia (NH3) (5.2 mg/L), electrical conductivity (EC) (449.9 μS/m), pH (8.9) and turbidity exceeding the acceptable limit of the Food and Agriculture Organization (FAO) and World Health Organization (WHO) standard. Nevertheless, the Wa Municipality generally have a very good groundwater potential both in quantity and quality to ensure sustainable irrigated agriculture. The findings of this study are set to be useful for planners, investors and policy makers for future decision-making regarding irrigation. For a full utilization, there is the need to monitor the groundwater quality especially the ammonia (NH3), electrical conductivity (EC), pH and turbidity. A further study to determine the heavy metals and biological parameters availability in groundwater for a safe irrigated agriculture is recommended