The Tungabhadra Dam is constructed across the Tungabhadra River, a tributary of the Krishna River. The dam is near the town of Hospet in Karnataka. It is a multipurpose dam serving irrigation, electricity generation, flood control, etc. This is a joint project of erstwhile Hyderabad state and erstwhile Madras Presidency when the construction was started; later it became a joint project of Karnataka and Andhra Pradesh after its completion in 1953.
The dam creates the biggest reservoir on the Tungabhadra River with 101 thousand million cubic feet (tmc) of gross storage capacity at full reservoir level (FRL) 498 m MSL, and a water spread area of 378 square kilometres. The dam is 49.5 meters high above its deepest foundation. The left canals emanating from the reservoir supplies water for irrigation entirely in Karnataka state. Two right bank canals are constructed — one at low level and the other at high level serving irrigation in Karnataka and Rayalaseema region of Andhra Pradesh. Hydropower units are installed on canal drops. The reservoir water is used to supply water to downstream barrages Rajolibanda and Sunkesula located on the Tungabhadra River. The identified water use from the project is 230 tmcft by the Krishna Water Disputes Tribunal. Karnataka and Andhra Pradesh got 151 tmcft and 79 tmcft water use entitlement respectively.As of August 2013, the project has an estimated capacity of 93.46 tmcft. The main architect of the dam was Dr. Thirumalai Iyengar, an engineer from Madras.
On the right side of the dam, tall Sanduru hill ranges extending up to 800 m MSL are close to the periphery of the Tungabhadra reservoir. These hill ranges form the Sanduru valley located above 600 m MSL. This reservoir is an ideal place to install pumped storage hydropower plants and lift irrigation projects. A moderate high level storage reservoir of capacity 20 tmcft at FRL 620 m MSL, can be constructed by damming the Sanduru valley. This reservoir will serve as upper pond and existing Tungabhadra reservoir as tail pond for installing pumped-storage hydroelectricity units. The water pumped during the monsoon months into the upper pond can be diverted by gravity to irrigate an extensive area in the uplands up to 600m MSL in Rayalaseema and Karnataka. This water can be pumped further to meet the drinking water requirements of Bengaluru city.
However, the available water resources at Tungabhadra dam are over-used, and water shortages are frequent. Water availability in the reservoir could be augmented by transferring water from the Krishna River, if a link canal were constructed from the Almatti / Narayanpur reservoir to the Tungabhadra reservoir. This canal would supply Krishna River water to the existing right bank canal of Tungabhadra dam and would augment water in Tungabhadra reservoir. Envisaging small balancing reservoirs where this link canal is intercepting the tributaries of Tungabhadra River would facilitate water diversion to Tungabhadra reservoir for further augmenting water availability. When this joint project of Karnataka and Andhra Pradesh is constructed, nearly 400 tmcft water additionally will be available for irrigation and drinking purposes in the high drought risk uplands of Rayalaseema and Karnataka.
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