Groundwater Quality Assessment and Monitoring Using Geographic Information Systems (GIS) in Port Harcourt, Nigeria

Abstract

The study evaluated the spatial variation of groundwater parameters in Port Harcourt metropolis using GIS. Thirty two (32) water samples were collected from boreholes from different parts of the study area into a treated and well labeled 1.5 litres plastic bootle. The water samples were then subjected to laboratory analysis for temperature, pH, Calcium (Ca²⁺), Chloride (Cl^-), Total Dissolved Solids (TDS), Nitrate (NO₃^-), Sulphate (SO₄^2-), Sodium (Na⁺), Potassium (K⁺), Magnesium (Mg²⁺), Electrical Conductivity (EC), Salinity, and bicarbonate (HCO₃^-). Global Positioning System (GPS) was used to record the latitudes and longitudes of the sampled boreholes. The result from the laboratory was subjected to descriptive statistical analysis in order to determine the mean, range and standard error of each parameter with the use of SPSS. Thereafter the result was imported to ArcGIS to generate the spatial variability maps for some groundwater parameters through the use of kriging in geostatistic module. Surfer 8 was used to generate the 2D and 3D representation of the borehole depths while Idrisi for windows was used to generate the relationship between borehole depth and pH ; and borehole depth and Ca. The result showed that Cl had the highest concentration among the anions with a mean value of 161.49 mg/l and Ca had the highest concentration among the cations with a mean value of 6.53 mg/l. The mean values of the all the groundwater parameters were lower than the WHO standard. Moderately weak inverse relationship was observed between the borehole depth and groundwater pH concentration; and between borehole depth and groundwater calcium concentration. It is recommended that the use of GIS should be encouraged to periodically monitor and assess groundwater quality.

Keywords: Borehole, Groundwater, GIS, Geostatistics, Port Harcourt