In contrast to the unfolding crisis in the Tungabhadra dam owing to high siltation, the State’s oldest dam, Krishnaraja Sagar (KRS) across the Cauvery, remains shielded from sedimentation.
The capacity evaluation of the KRS conducted in 2009 indicates that the 85-year-old reservoir has lost barely 6.7% of its storage capacity. A new study using remote sensing satellite and GPS applications is under way, but it may take up to three years for its completion, according to officials.
Officials attributed the relatively negligible silt accumulation in KRS to the geographical terrain of the Cauvery in the upstream region. “The river flows through rocky terrain from Talacauvery in Kodagu district before it is impounded at the KRS. A major portion of the catchment of the river — spread over 10,619 sq. km — is in the upstream region, which has rocky and hilly terrain with thick forests, as a result of which the water does not carry much silt compared with rivers flowing through the plains,” an official said.
The total silt accumulated in 85 years was pegged at 3.318 tmcft, less than 10% of that accumulated in the Tungabhadra dam. However, officials point out that accumulated silt in the KRS also includes tonnes of rocky debris left behind at the dam site to act as wave-breaker, a safety feature to reduce the intensity of surging waters.
