AQUIFER VULNERABILITY ASSESSMENT USING DRASTIC AND GIS IN DAMATURUMETROPOLIS, YOBE STATE, NIGERIA

Abstract

The study employed DRASTIC model and Geographic Information System (GIS) technology to assess the intrinsic groundwater aquifer vulnerability to contamination in Damaturu Metropolis, Nigeria. The DRASTIC index model uses seven (7) environmental parameters; depth to water level, net recharge, aquifer media, soil media, topography, impact on vadose zone and hydraulic conductivity for the assessment of intrinsic aquifer vulnerability. The DRASTIC scores obtained vary from 81 to 153 which was classified into four vulnerability zones i.e. low, moderate, high and very high. The GIS analysis shows that of the total area of Damaturu Metropolis, about 8.5% was classified as “Low Vulnerability”, 66% as “moderate vulnerability”, 18.8% as “high vulnerability” and 6.7% as “very high vulnerability”. The validation of the DRASTIC model was achieved through comparison between the DRASTIC vulnerability index map and nitrate concentrations of 52 borehole water samples in the area and using Pearson’s (r) correlation coefficient equation. It was found that r = 0.7 which indicates a significantly high correlation between the vulnerability index and nitrate concentration values. Overall, this study produced a very valuable tool for the state agencies responsible for groundwater resource management, environmental protection and planning because it can be very useful in planning and siting activities that generate pollutants (e.g., sanitary landfill, soak away, automobile workshops and petrol station) which pollute the groundwater, in determining where groundwater protection or remediation efforts be directed to, thereby reducing the overall cost of groundwater monitoring in Damaturu metropolis.