2-Water budget of drinking water supply sources - Osmansagar and Himayatsagar Lakes Hyderabad

Abstract

Osmansagar and Himayatsagar lakes are serving the drinking water needs of Hyderabad city. The lakes have been built around 1920's to cater the need of entire population of Hyderabad. Lakes are built on Musi and Musa rivers draining on southwestern part of the city. The salient features of Osmansagar lake on Musi river include storage capacity of 115 mcm at FRL 545.59 m during 1976 with a loss of about 64 mcm due to siltation. The lake has a catchment area of 736 sq km with 637 sq km of free catchment and rest has been intercepted. Himayatsagar lake on Musi river has a capacity of 115 mcm and has a catchment area of 1340 sq km. The Osmansagar and Himayatsagar lakes have been formed on 6th & 5th order streams respectively. A number of check dams have been constructed on first and second order streams under various government schemes during last 5 years. The indiscriminate constructions have resulted in reduction of storage volumes in the lakes. Lakes were receiving about 20 —25 mcm of base flow from the stream channels entering them during monsoon and up to November/December. Preliminary assessment of impact of the check dams on water resources in the catchment has showed that base flow component has reduced, whereas significant reduction in the surface runoff of streams draining into the lakes has been observed. The sustainable drinking water supply from the lakes have been at stake due to human intervention, forcing the government to search for alternate sources of drinking water supply to Hyderabad. A comprehensive watershed development programs has to be planned without endangering existing sustainable water supply sources to urban areas in the country in future.