Krishna Raja Sagara, also popularly known as KRS, is the name of both a lake and the dam that creates it. It is located close to the settlement of Krishnarajasagara in the Indian State of Karnataka. The gravity dam made of surki mortar is situated below the confluence of river Kaveri with its tributaries Hemavati and Lakshmana Tirtha, in the district of Mandya
The region of Mysore and especially Mandya had historically been dry, and had witnessed mass migration to adjoining areas in the hot summers. A severe drought in 1875–76 had wiped out one-fifth of the population of the Kingdom of Mysore. Crop failures were common due to lack of water for irrigation. The Kaveri River was seen as a potential source of irrigation water for the farmers in and around Mysore in the erstwhile Kingdom of Mysore.
The Chief Engineer of Mysore M. Visvesvaraya presented a blueprint to build a dam across the River near the village of Kannambadi. However, he was faced with opposition from the finance ministry of the government of Mysore who said the project would "serve no purpose" and that the electricity produced from it would not be of complete use due to lack in demand. He then approached T. Ananda Rao, the Diwan of Mysore and the Maharaja Krishna Raja Wadiyar IV for a reconsideration. Upon examining, the latter gave his consent issuing an order on 11 October 1911 to begin the project and a sum of ₹81 lakh was set aside for it. Madras Presidency then opposed the project and urged the imperial government to not approve it. Upon Visvesvaraya's persuasion, the government consented. However, the initial plan of wanting to build a dam of 194-feet high to hold an estimated 41,500,000,000 cu ft (1.18 km3) of water had to be dropped.
Construction began in November 1911 and 10,000 workers were employed. A mortar known locally as surki was used in place of cement as the latter was not manufactured in India at the time, and importing would prove costly for the state.  By the time construction completed in 1931, around 5,000 to 10,000 persons had lost their homes to the project. However, they were rehabilitated and provided with agricultural land in the adjacent areas by the government.
text matter from - https://en.wikipedia.org/wiki/Krishna_Raja_Sagara