Socioeconomic and recharge effect on spatial changes in the groundwater chemistry of Punjab, Pakistan: a multivariate statistical approach

Abstract

This study presents deterioration in groundwater quality of highly populated region of Punjab Province, Pakistan, by linking chemical data with rain, river recharge, and socioeconomic factors. Various chemical parameters like total dissolved solid (TDS), arsenic (As), fluoride (F−), Iron (Fe), nitrate (NO3−), nitrite (NO2−), and pH were determined for 46,457 samples collected from 205,344 km2 area of the Punjab. The samples were collected, stored, and analyzed as per the Environment Protection Agency (EPA) methods at laboratory. Commercial kits were used for analysis of Fe, As, NO2−, NO3− and F−, while TDS and pH were measured by respective meters. Chemical parameters were correlated with human and animal population, fertilizers consumption, tube wells, industrial density, rain occurrence, and river recharge rate. Data were analyzed using XLSTAT, and GIS 10.3 was used to draw the maps. Spatial classification of the districts was performed by principal component analysis and hierarchal cluster analysis. TDS, As, F−, Fe, NO3−, NO2−, and pH were found to be 50–52,360 mg/L, 0–735 μg/L, 0–121 mg/L, 0–37.2 mg/L, 0–2215 mg/L, 0–3033 mg/L, and 0.09–10.9, respectively. The study revealed that 66.26% of the samples were fit for drinking purpose, while 33.74% were unfit. Further, it was found that 27% of the samples were non-saline, 26% were saline, and 47% were slightly saline based on the World Health Organization drinking water quality criteria. A nonlinear model was developed which explains 57% of variance in groundwater quality. Based on groundwater quality, the whole province was divided into three main regions: northwestern districts, central districts and southeastern districts. Central Punjab was highly polluted, followed by southeast region, while northwest Punjab has better quality water due to more rains and Indus River. Current study provides a model to predict future water quality of the region and suggests that new water canals in southeast Punjab can improve water quality. Moreover, it is recommended that agriculture and industrial effluents should be controlled to improve water quality, new smart cities should be built along Indus River, and population should be controlled in southeast and central Punjab.Graphical abstract