Srisailam Dam

The Srisailam Dam is a gravity dam built on the confluence of Tungabhadra River and Krishna River. Its hydroelectric power station is India's 2nd largest by capacity. It is located in the Nallamala Hills near the temple town Srisailam. The dam spans a deep gorge between the districts Nandyal (Andhra Pradesh) and Nagarkurnool (Telangana). It has a maximum height of 143 metres (470 ft) and a length of 512 metres (1,680 ft). The reservoir has a surface area of 616 square kilometres (238 sq mi) and a gross storage capacity of 216 tmcft (6.1 km3). The active storage capacity is 178.74 tmcft (5.061 km3) corresponding to the full reservoir level at 270 metres (885 ft) MSL. The minimum draw-down level of the reservoir is at 215 metres (705 ft) MSL and the corresponding dead storage is 3.42 tmcft (0.097 km3). There are two turbine halls: an underground building on the left bank with six 150 MW (200,000 hp) reversible Francis-pump turbines for pumped-storage operation (each turbine can pump 200 m3/s) and a semi-underground building on the right bank with seven 110 MW (150,000 hp) Francis-turbine generators. A 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 hydropower stations. Tail pond weir was completed during the year 2017 and pumping mode operation is being done even when the downstream Nagarjuna Sagar reservoir water level is below 531.5 feet (162 m) MSL. The tail pond has nearly 1 tmcft (0.028 km3) live storage capacity.