Physico-chemical status of groundwater near Varuna river in Varanasi city, India

The Varuna is a minor tributary of the Ganges and extended between 25°27’ N to 82°18’E and 25°45’ N to 82°3’ E flows east to southeast from some of 100 km from Phulpur tehsil of Allahabad and joins the Ganges at 25°19’ N 83°2’ E and 25° 32’ N 83° 44’ E just downstream of Varanasi. The lower Varuna river basin in Varanasi district situated in the central Ganga plain is a highly productive agricultural area and also one of the fast growing urban areas in India. The agricultural and urbanization activities have a lot of impact on the ground water quality of the study area. The study area is underlain by Quaternary alluvial sediments consisting of clay, silt, sand and gravel of various grades. The hydrogeochemical study was undertaken by randomly collecting 12 groundwater samples from dug wells and bore wells covering the entire area in order to understand the sources of dissolve ions and to assess the chemical quality of the promoting agricultural production and standard of human health. It is found that over exploitation of groundwater has detrimentally affected groundwater in terms of quality and quantity. Most groundwater samples are suitable for irrigation except one sample (sample no. 12). Although the general quality of groundwater of the lower Varuna river basin is suitable for irrigation purpose, forty one percent of the samples are found having nitrate content more than permissible limit (>45mg/L) which is not good for human consumption. Application of N-fertilizers on agricultural land as crop nutrients along the Varuna river course is responsible for nitrate pollution in the groundwater due to leaching applied irrigation water. The other potential source of high nitrate concentration in extreme northern, southern and southwestern parts of study area are poor sewerage and drainage facilities, leakage of human excreta from very old septic tanks, and sanitary landfills.