An analytical hierarchy process-based geospatial modeling for delineation of potential anthropogenic contamination zones of groundwater from Arang block of Raipur district, Chhattisgarh, Central India

In the present study, identification of groundwater zones that are affected by anthropogenic contaminants based on litho-hydrogeological parameters has been attempted using multi-criteria decision analysis-analytical hierarchy process (MCDA-AHP) technique in an agriculturally intensive Arang block of Raipur district, Chhattisgarh, Central India. Litho-hydrogeological factors, such as geological and aquifer characteristics, land use-land cover, depth to water table, soil type, rainfall distribution, slope, geomorphological features, drainage density, elevation and lineament density parameters are considered for the delineation of anthropogenic contamination zones based on an integrated index model in Arc-GIS. Various input layers were assigned weights and then weight normalization process was adopted using Saaty's AHP method to develop the integrated potential anthropogenic contamination zone (PACZ) map, based on the relative importance of anthropogenic contamination of groundwater. According to the proposed model majority of the study area falls under precarious zone, though certain areas fall under safe zone. In course of time, without proper planning the area could turn out to be moderately unsafe to unsafe zone. The PACZ map was validated with the fluoride concentration in groundwater as per National Rural Drinking Water Programme (NRDWP) report along with the measured nitrate concentration values. Model accuracy was achieved by agreement of about 82% of the fluoride values and 94% of the nitrate values with the proposed output map. Further validation of the model with fluoride and nitrate data was performed using computing similarity analysis with Pearson's correlation coefficient which suggests anomalously higher concentrations of fluoride and nitrate ion concentration in certain areas of Arang block, which could be emanated from non-point anthropogenic sources. Additionally, Gibbs's plot and saturation indices of fluorite and calcite suggest that groundwater chemistry is primarily controlled by aquifer lithological characteristics (rock-water interaction) and diffused anthropogenic contamination sources.