The biggest impact is being seen at the Tungabhadra (TB) reservoir in Vijayanagar, which has accumulated 31.6 TMC of silt, the highest among dams. Basavasagar (Narayanpur) in Yadgir has 10.5 TMC. But in terms of storage loss, Basavasagar is the worst affected, with a 28% reduction in capacity, while the TB dam has lost 24%.
Despite a good monsoon this year, the shrinking storage capacity of Karnataka’s reservoirs due to heavy siltation has emerged as a major concern. National standards permit silt levels of up to 3% of a reservoir’s capacity, but several dams have already reached or crossed that limit.
A water resources department analysis shows that the state’s 10 major dams have lost an average of 12.5% capacity, with individual losses ranging between 4% and 28%. Experts warn that unchecked siltation could impact agriculture, horticulture, power generation, and industries, while climate change and erratic rainfall may further accelerate the problem.
Massive challenge of desilting
Officials point out the scale of the issue. TB dam, which stretches 21 km, receives 0.4 TMC of silt annually and has accumulated nearly 32 TMC over 70 years, almost equal to the entire storage of Krishnarajasagar (KRS). To remove this and dump it in 10-foot mounds would require over 73,000 acres of land. Even with 1,000 tractors removing 1 TMC per day, the task is deemed unfeasible.
The impracticality was evident in 2017 when farmers attempted a community-led desilting drive using tractors, tippers, and backhoes. After two weeks of hard work and spending ₹15 lakh on fuel and food, the silt was dumped on nearby farmlands, but the effort was soon abandoned.
The state had submitted a proposal to the Centre to remove 26 TMC of silt at a cost of ₹13,695 crore, but the project has not progressed. Meanwhile, Karnataka is awaiting nods from Andhra Pradesh and Telangana to construct a balancing reservoir.
“Unlike TB dam, which is nearly 75 years old (built in 1950), Basavasagar was built in 1982 and is already losing storage at a rapid pace,” a retired water resources official said. “This situation only helps downstream states as surplus water flows away, depriving our farmers.”