169-Water Supply to Patna through River Bank Filtration - Problems and Prospects

Abstract

Patna, the capital of the State of Bihar in India, is situated on the bank of Ganga, a major perennial river, with a population currently of 1.7 million with an increasing trend. The source of water supply to Patna has exclusively been groundwater from confined aquifer extending from 100 m to 300 m extracted by a number of deep tubewells. On account of falling water levels in the tubewells, water supply to the city is getting stressed particularly during summer months. There may also be environmental hazard due to overexploitation. Hence augmentation of water supply to Patna from another source is a prime need. The obvious alternative of using the river water is presently ruled out primarily due to heavy recurring cost of treatment required. In this context, the technique of River Bank Filtration (RBF) seemed prospective. A two-year project on investigating the technical feasibility of RBF at Patna was carried out by Integrated Hydro Development Forum, Patna under European Cross Cultural Programme of European Union. The lithological investigations showed that the deep aquifer supplying water to Patna is connected to the river through a thick sand layer formation under the river bed. This connectivity is corroborated by simultaneous water level and water quality observations of the river and tubewells. Also, there are good aquifers at shallow depths in selected bands in Patna, representing abandoned courses of river Sone which are possibly potential sites of RBF on river Ganga. Further investigations including isotope studies and pilot projects are recommended to confirm connectivity of aquifers with the river and to establish tecnno-economics of RBF at Patna for augmenting it's stressed water supply