Silt threat to Srisailam dam

Silt threat to Srisailam dam
Highlights

Reduction of storage capacity at Srisailam project as a result of Increasing sedimentation is worrying engineers no end. Nearly a dozen irrigation projects and hundreds of drinking water schemes, including the Telugu Ganga, are faced with the threat of reduced storage capacity. It has caused a loss of 46 tmcft out of the total storage of 308 tmcft. The sedimentation at Srisailam has risen by 0.856 per cent a year as against the natural sedimentation of .5 per cent. The original reservoir capacity of Srisailam is around 8723.09 million cubic meter (MCUM) and it was reduced to 6110.9 MCUM. The reduction amounts to 2,612.19 MCUM. The capacity loss of Srisailam in 1984 was 2013.33 MCUM.

  • Sedimentation more than that in other projects
  • Siltation removal will cost more than project cost
  • If neglected, project would have to be abandoned
  • Dams cannot be reconstructed at the same site

A Ravindra Seshu

Hyderabad : Reduction of storage capacity at Srisailam project as a result of Increasing sedimentation is worrying engineers no end. Nearly a dozen irrigation projects and hundreds of drinking water schemes, including the Telugu Ganga, are faced with the threat of reduced storage capacity. It has caused a loss of 46 tmcft out of the total storage of 308 tmcft. The sedimentation at Srisailam has risen by 0.856 per cent a year as against the natural sedimentation of .5 per cent. The original reservoir capacity of Srisailam is around 8723.09 million cubic meter (MCUM) and it was reduced to 6110.9 MCUM. The reduction amounts to 2,612.19 MCUM. The capacity loss of Srisailam in 1984 was 2013.33 MCUM.

This has come to light during surveys conducted by the Central Water Commission (CWC) and the Andhra Pradesh Engineering Research Laboratories. Moreover, studies over the years have shown that the silt gets deposited in both the dead storage (the storage at the bottom, below the Minimum Draw Down Level, which is not used under normal circumstances) and in the Live Storage (LS). This process of accumulation of silt in the reservoirs is called siltation.

The sedimentation of Srisailam is more when compared to that at Nagarjunasagar and Sriramsagar irrigation projects. Reduction per year of Sriramsagar is 0.796 per cent and Nagarjunasagar is 0 .547 per cent. The findings have dismissed the belief among engineers that Krishna-based projects are free from siltation as the river passes through "rocky" terrain compared to the Godavari which "dumps" huge deposits of black cotton soil at the dams with Sriramsagar reduced by nearly one-fifth of its storage capacity.

C Chandrasekhara Rao, a retired engineer said, “Tackling sedimentation is a big problem and it would cost more than the cost of the project.” He said that the storage capacity would be more in the coming years.

Gregory Morris (author of Reservoir Sedimentation Handbook, 1997) in a paper presented at the Sixth International Symposium on River Sedimentation in New Delhi in 1995 wrote: “Dams cannot be reconstructed at the same site once the reservoir has filled with sediment; the sediment must either be removed or the site abandoned. The cost of sediment removal at a large reservoir can easily exceed the original dam construction cost by an order of magnitude.”

Show Full Article
Download The Hans India Android App or iOS App for the Latest update on your phone.
More Stories


Top