Groundwater vulnerability assessment using water quality index (WQI) under geographic information system (GIS) framework in parts of Uttar Pradesh, India

Groundwater resources are affected in principle by three major activities. First is excessive use of fertilizers and pesticides in agricultural areas. The second is untreated/partially treated wastewater to the soil/water and the third one is excessive pumping and improper management of aquifers. Due to large-scale urban growth which has triggered domestic effluents and on the other hand industrial development activities has resulted in the generation of a copious volume of industrial effluents directly and indirectly contaminate the groundwater. In a drinking water quality assessment, the decision-making based on water quality data is a crucial issue because several parameters compromise its quality. There has been considerable advancement in the field of water quality assessment particularly based on the principle of the water quality index (WQI) using modified concepts. The study area which includes part of Varanasi and Sant Ravidas Nagar districts are centers for urban growth along with industrial setup in Uttar Pradesh, India. Water quality index (WQI) is an index reflecting the composite influence of different water quality parameters which is considered for calculation. 50 numbers of groundwater samples were collected from various locations in the study area as per the standard protocol prescribed by the American Public Health Association (APHA). Twenty-two water quality parameters have been considered for the calculation of water quality index viz. pH, electrical conductivity (EC), total hardness (TH), total dissolved solids (TDS), alkalinity, sodium (Na+), potassium (K+), calcium (Ca2+), magnesium (Mg2+), nitrates (NO3-), bicarbonate (HCO3-), chlorides (Cl-), sulphates (SO4-), fluorides (F-), chromium (Cr), zinc (Zn), copper (Cu), manganese (Mn), iron (Fe), nickel (Ni), lead (Pb) and cadmium (Cd). The Bureau of Indian Standard has been considered to assess the suitability of groundwater for drinking purposes and the calculation of the water quality index (WQI). Correlation study among various physicochemical properties also reflects certain significant negative relationships. The current study shows that 50% of the collected water samples are non-suitable for the drinking water category and the rest is falling under the good, moderate, poor, very poor as per the Water Quality Index (WQI) classification. The present study is quite helpful for the proper planning and management of available water resources for drinking purposes.