A new study shows that two federal reservoirs in Kansas are losing significant amounts of water storage capacity to sediment.

The U.S. Geological Survey says Kanopolis and Tuttle Creek reservoirs are retaining at least 95% of the sediment that flows into them. Water storage at Kanopolis, located outside Salina, was down 34% as of 2010. Tuttle Creek storage has dropped 43%.

The study, conducted by USGS and the Kansas Water Office, looked at sediment data from 2008 to 2010 and found that much of the sediment came from the banks of upstream waterways.

Kanopolis and Tuttle Creek reservoirs were built more than 50 years ago for water storage, flood control and recreation.

The USGS says the study demonstrates that the man-made reservoirs are meant to last “mere decades.”