29-Environmental impact assessment of urban lakes on ground water regime in Hyderabad city

Abstract

Hyderabad metropolis is one of the fastest growing populations in India and has previously relied on surface water storages in lakes for urban water supply. Reported impacts on groundwater around Hyderabad urban agglomeration are varied and include: changes in land use from agriculture to residential/industrial, declining water tables, worsening water quality in lakes due to nutrient flows (urban sewage). One of the problems tackled under restoration of lakes program by Hyderabad Urban Development Authority is characterization of groundwater regime around lakes. Studies in three urban lakes watersheds, viz., Lakes in Northeast Musi basin, Durgamcheruvu and Mir-Alam- Tank have been carried out to monitor the groundwater contamination of nitrate, if any in the command areas. Bathymetric studies have helped find out the lake water storage. Lake water quality in terms of nutrients Total Phosphorous and Total Nitrogen have helped to compute Trophic Status Index. All the lakes under investigation are under hyper eutrophic condition. The hydrological features of the lakes, associated hydrogeological aspects, importance groundwater conditions on water quality in the NE Musi basin has been investigated to establish interactions between lake water and groundwater system. The integrated geophysical and hydrogeological investigations have provided an insight of the complex nature of groundwater contamination in the basin. Groundwater occurs in shallow aquifers in granitic terrain, some limited in extent and some susceptible to impacts from urban development, industrialization as well as from natural processes in the area. Water balance has been evolved through groundwater flow modeling to compute interaction of the lake water with the groundwater regime. A tertiary treatment plant removes phosphates and associated wetland reduces the nitrates and treated sewerage enters the lake with less nutrient inputs. The lake water budget has helped to decide the capacity of sewage treatment Plant (STP) for tertiary treatment to be established on each lake in the watershed.