Sediment Buildup Removes Vital Water Capacity For Drought Years

SACRAMENTO (CBS13) — Sediment built up in reservoirs could be hurting the amount of water California can save ahead of a drought.

As sediment settles at the bottom of the reservoirs, it limits the amount of water that can be saved in them. As a result, more water ends up released during wet winters that could be saved for dry summers.

"The ultimate fate of every dam is to be filled with sediment," said Jay Lund, the director of the Center for Watershed Sciences. "[Sediment] comes down and when it hits a reservoir, it will fall out when the water slows down."

During the wet years, the buildup isn't as noticeable, but in droughts like our current one, a common question comes up: Why not remove that sediment to make more room for water in the future?

Lund estimates that dredging will cost 10 times more than building the dams higher.

"If you had the choice of expanding most reservoirs by raising them or dredging out sediment, I think you'd typically find that the economics support raising the reservoirs," he said.

Luis Moore with the Bureau of Reclamation says his agency agrees with the calculations.

"Not only the amount of trucks required, but the time required and then where do you put the sediment once it has been excavated," he said.

Lawmakers are pushing for water bonds that pay for more surface storage of water. Shasta Lake, which accounts for one-sixth of the state's water capacity, is at the top of the expansion list.

"If you are going to be spending billions of dollars in public money, we should be looking at what are we really going to get for this. And is this the best way to invest?" Lund said.

The Bureau of Reclamation estimates Folsom Lake sediment amounts to about a 3 percent loss of water storage—or the equivalent of losing water for 43,000 families a year.