18-Restoration of Urban Lakes in Hyderabad Lakes in NE Musi Basin

Abstract

Hyderabad is beautiful city of chain of lakes connected to one another. Unfortunately over the years the lakes have started receiving urban sewage and causing problems of eutrophication. A chain of six lakes drains the North East Musi Basin over a distance of 12 km length. The groundwater monitoring has been carried out to assess the impact of lake water quality on groundwater conditions. The BOD, COD, Total Phosphorous (TP), Total Nitrogen (TN) of lake water and sediment adsorbed TP and TN have been measured through bimonthly sampling since October 2002. As regards lake water quality• all lakes have attained hyper eutrophic conditions. The trophic state index (TSI) of TP and TN showed that the lake water is nitrate limiting.

The major ion analyses in the NE Musi Basin shows hydro-chemical pattern correlates with the flow pattern of groundwater in the basin. Low total dissolved solids concentration, high Calcium: Magnesium ratio, low sulphate and high bicarbonate occur in the headwater lakes area, whereas opposite conditions are associated in the down stream lakes area. In terms of hydro-chemical species, the ground waters of Na-Ca-CI-HCO3 and Ca-Mg-Na-CI-HCO3 types are dominant between RK Puram cheruvu and Bandacheruvu, and those of the Na-Ca-CI- HCO3-SO4 are dominant between Patelcheruvu and Peddacheruvu, Na-Ca-Mg-HCO3-Cl between Peddacheruvu and Nallacheruvu and below Na-Mg-C1 under Nallacheruvu. As regards surface waters the upstream three lakes possess Ca-Mg-HCO3-CI type and the rest three down stream lakes are of Na-Mg-Ca-CI-HCO3-SO4 type. The hydro-chemical evolutionary trends appear to be strongly related to the groundwater flow paths. Five facies of groundwater has been identified in the NE Musi basin Na-Ca-CI-HCO3, Ca-Mg-Na-C1-HCO3, Na-Ca-CI-HCO3-SO4, Na-Ca-Mg-HCO3-CI and M.-Mg-CI respectively along the flow path. Whereas the young waters of facies 1 and 2 are associated with the headwater lakes area and the third type is dominant due to human interventions in the central part of the basin and 4 and 5 types of geo-chemical facies are dominant in the valley bottom. Groundwater flow model has helped to compute seepage losses from the lakes and thereby deciding capacity of sewage treatment plants to be installed on each lake. -