Spatial analysis of groundwater suitability for drinking and irrigation in Lahore, Pakistan

This study used a total of 474 groundwater samples analyzed from 2014 data to evaluate the distribution of groundwater quality in the Water and Sanitation Agency (WASA) jurisdiction of Lahore city, Pakistan. The study further assessed the variations in suitability of groundwater for drinking (emphasis on arsenic and fluoride) and irrigation using spatial correlation technique in GIS. The hydrochemical analysis revealed a predominance of Mg-Ca-HCO₃-SO₄ and Ca-Mg-HCO₃-SO₄ type. Distribution analysis indicated relatively higher salinity (TDS_max = 1667 mg/L), total hardness (TH_max = 558 mg/L), and alkalinity (HCO₃^-_max = 584 mg/L) in the south-eastern region of the city, while the central part displayed the highest levels of SO₄ and NO₃. Also, the eastern region (north-south) of Lahore had significantly elevated As concentrations (up to 86 μg/L). The order of exceedance in terms of arsenic was Gunj Bakhsh town (17.4%), Nishter town (16.4%), Iqbal town (9.8%), Aziz Batti and Shalimar town (8.1%), and Ravi town (3%). The groundwater was classified as average saline to highly saline, except few samples in Aziz Batti/Shalimar town that were in non-saline group. Otherwise, the various indices classified the groundwater for irrigation as generally acceptable. With the various irrigation quality indices displaying discernible variations for the entire study area, it was observed from the distribution maps that the groundwater suitability for irrigation is relatively excellent in the areas away from industries and landfill locations. Also, the chloride analysis shows 98.7% of the groundwater samples belong to the very fresh and fresh water class. Thus, continued monitoring and studying the changes in groundwater quality in Lahore is imperative.