Application of GIS in the Assessment of Groundwater Quality in the Yenagoa Watershed of the Niger Delta Region of Nigeria

The spatial variations in groundwater quality in parts of the Yenagoa watershed (YWS) in the Niger Delta Region of Nigeria has been investigated using Geographic Information System (GIS). An understanding of the factors responsible for groundwater vulnerability could facilitate the use of geographic information system in the control and management of groundwater quality. This study is due to the fact that the spatial distribution maps of groundwater quality in the YWS obtained by GIS modeling are not documented. The quality of groundwater accounts for the environmental and human health status of the residents in the YWS. Therefore, twenty (20) water samples obtained from shallow boreholes were analyzed for physicochemical properties. The physicochemical parameters such as pH, conductivity, total dissolved solids, sulphate, nitrate, sodium, chloride, magnesium, total hardness and iron contents were measured using standard laboratory procedure. Except for the iron content, the results obtained from the physicochemical analyses were within limits of the World Health Organization Standards for drinking water. These results were transformed into spatial distribution maps using GIS modeling and interpretation. The Index Overlay method and Inverse Distance weighted method form component parts of the GIS modeling used in the generation of the spatial distribution maps for each physicochemical parameter. These modeled results were related to the World Health Organization (WHO) Standard for drinking water. The maps generated from GIS modeling indicated zones that were suitable for groundwater extraction as opposed to zones unsuitable for groundwater extraction. In conclusion, 55% of the boreholes in the Yenagoa watershed were affected by high iron content.