Groundwater quality assessment using the potability water quality index (PWQI): a case in the Kashan plain, Central Iran

During the last few decades, a number of industrial and agricultural developments have occurred in Kashan plain which have led to uncontrolled groundwater depletion and water quality deterioration. The present study is aimed at assessing suitability of groundwater quality in the study area using the potability water quality index (PWQI) which includes human acceptability measurements. Groundwater samples were collected from 18 locations in the study area and analyzed for their physicochemical parameters, i.e., pH, electrical conductivity (EC), total dissolved solid (TDS), total hardness (TH), calcium (Ca²⁺), magnesium (Mg²⁺), sodium (Na⁺), potassium (K⁺), bicarbonate (HCO₃⁻), sulfate (SO₄²⁻), and chloride (Cl⁻), to calculate the PWQI. Using this index, the sampling results indicate that 22.2 percent of samples can be classified as being “good” and acceptable for drinking consumption, while 27.8 percent of water samples are “fair” in quality and the rest of samples are “marginal,” “poor” or “very poor” in quality and unsuitable for drinking and require treatment before consumption. A sensitivity analysis of the PWQI results indicated that HCO₃, pH, Ca, and Mg and pH have a significant impact on the PWQI calculation. The sensitivity of the PWQI to the changes of the sub-index values from 10 to 100 shows that HCO₃, Ca, Mg, and Na with approximately 31.7% variation in the PWQI value have the most impact on the PWQI, while the least sensitivity of the PWQI is related to the sub-index values of K.