The Srisailam Dam is constructed across the Krishna River in Kurnool district, Andhra Pradesh near Srisailam temple town and is the 2nd largest capacity working hydroelectric station in the country. The dam was constructed in a deep gorge in the Nallamala Hills in between Kurnool and Mahabubnagar districts, above sea level. It is long, maximum height and has crest gates. It has a reservoir of. Project has an estimated live capacity to hold 178.74 Tmcft at its full reservoir level of MSL. The minimum draw down level of the reservoir is at MSL from its river sluice gates and corresponding dead storage is 3.42 Tmcft. The left bank underground power station houses reversible Francis-pump turbines for pumped-storage operation and the right bank semi under ground power station houses Francis-turbine generators. Tail pond dam /weir located 14 km downstream of Srisailam dam is under advanced stage of construction to hold the water released by the hydro turbines and later pump back into the Srisailam reservoir by operating the turbines in pump mode. The weir portion got breached in November 2015 unable to withstand the normal water release from the hydro power stations. Tail pond weir was completed during the year 2017 and pumping mode operation is being done even the downstream Nagarjuna Sagar reservoir water level is below MSL. The tail pond has nearly 1 tmcft live storage capacity.
Project history
The Srisailam project began in 1960, initially as a power project. After several delays, the main dam was finally completed twenty years later in 1980 July 26. In the meantime the project was converted into a multipurpose facility with a generating capacity of by its second stage which was completed in 1987. The dam is to provide water for an estimated. Under the right bank branch canal in Kurnool and Kadapa districts will have assured irrigation. From the initial modest estimate of for a power project the total cost of the multipurpose project was estimated to cross in its enlarged form. The dam has alone cost together with the installation of four generating sets of each. The right bank branch canal is estimated to cost and the initial investment of has been provided by the World Bank. The projected cost-benefit ratio of the project has been worked out at 1:1.91 at 10% interest on capital outlay.. In 1998 a coffer dam was over topped by flooding. The power house required repairs and did not generate power for a year. On 2 October 2009, Srisailam dam experienced a record inflow which threatened the dam.
Systematic Neglect and absence of diversion of funds is evident in maintenance of the dam and lack of any modernization attempts of the Powerhouse. The officers report a shortage of maintenance staff. Safety concerns to the 2nd largest Hydroelectric project in the country have been raised over the years and have been assessed false subsequently. In 2009, the dam, designed for a maximum flood of 19 lakh cusecs, endured a flood of 25.5 lakh cusecs. According to a survey conducted in summer of 2018, the scouring resulted in the formation of a huge pit in the apron downstream the dam. And a structure protecting the ‘toe’ and foundation of the main dam has weakened. Efforts are not yet made to repair and maintain the dam.
At present the initial inflows into Srisailam reservoir are stored excessively without using for power generation. The flood water fills the remaining empty Srisailam reservoir quickly and most of the flood water overflows into downstream Nagarjunasagar reservoir without being used for power generation. The endeavor shall be to fill the Nagarjunasagar reservoir fully with the uniform water released through the power generating units.
