Comparison of stochastic and traditional water quality indices for mapping groundwater quality zones

Abstract

This study has compared the use of standard water quality overlay techniques with that of Getis-Ord Gi* statistical techniques for visualizing the spatial distribution of water quality parameters in an unconfined aquifer beneath the city of Lahore in Pakistan. The non-uniformly distributed groundwater sampling points were uniformly transformed to a grid of evenly distributed values to apply Getis-Ord Gi* statistics. An optimized neighborhood distance value of 700 m was determined for the Getis-Ord Gi* assessment, showing that the aquifer is regionally continuous and there are no barriers to lateral groundwater flow. This statistical approach was initially applied to individual parameters and was found to better define hotspots than that of the conventional method. Similarly, the use of Getis-Ord Gi* values improved the assessment of hotspots of water quality index (WQI) values than conventional overlay techniques.