Seasonal changes in groundwater quality and its suitability for drinking and irrigation uses

Abstract

This study deals with evaluation of spatial and short-term temporal variation of groundwater quality during pre- and post-monsoon seasons in Jaipur district of Rajasthan by using statistical techniques, i.e. box and whisker plots, correlation matrices, and t-test, to the data collected for 153 sampling sites. In addition, this study assesses the groundwater quality to find its aptness for drinking and irrigation needs by comparing with drinking water standards prescribed by World Health Organization (WHO), and by plotting United States Salinity Laboratory (USSL) diagrams. Data of 13 groundwater quality parameters, i.e. calcium, magnesium, sodium, potassium, sulphate, chloride, nitrate, carbonate, bicarbonate, fluoride, total dissolved solids (TDS), electrical conductivity (EC) and pH, were analyzed for two seasons of four-year (2006-2009) period. The box and whisker plots revealed presence of non-normality in spatial series of almost all the parameters due to right-skewed distributions in both seasons. The box-whisker plots also revealed linkages between the water quality parameters and rainfall recharge occurring in aquifer system. Correlation matrices depicted a very strong linear relationship between seven pairs of the groundwater quality parameters, i.e. EC-TDS, EC-sodium, EC-chloride, TDS-sodium, TDS-chloride, pH-carbonate, and sodium-chloride during both seasons. However, magnitude of correlation was relatively less during the post-monsoon season as compared to pre-monsoon season. Results of t-test revealed a significant change in the mean concentrations of six parameters, i.e. pH, sodium, calcium, bicarbonate, nitrate, and fluoride at 5% significance level during pre-monsoon season in 4-year period. On the other hand, during post-monsoon season, only nitrate showed a significant change in 4-year period. Moreover, the groundwater quality in the area is not found safe for drinking purpose based on WHO standards as well as for irrigation use based on USSL diagrams. This finding emphasizes the need of formulating adequate policies in order to preserve and improve the groundwater quality in the area.