SACRAMENTO, Calif. — No matter if it's a dry year or wet year, there are continued pleas for more water storage. Now, an American River Basin study is showing how a strategically placed high Sierra reservoir might be part of the water solution.
The concern to capture Sierra runoff is seeing increased interest as California experiences even bigger climate whiplash years - going from droughts to floods.
The big snowpack in the Sierra this year stands out as an anomaly with climate models forecasting more rain than snow falling in the lower mountains by the end of the century. The other concern is the earlier runoff and having to store and manage reservoir water over a longer period of time through the dry summer months.
To help ease that tension, a new reservoir is being considered near Alder Creek in the Sierra. This is just above Pollock Pines in El Dorado County just off Highway 50.
Rebecca Guo with the El Dorado Water Agency says this strategically placed reservoir would be able to capture water during large rain events and also Sierra snowmelt, increasing Folsom's total water supply by about 18%. Since the water would be held upstream from Folsom Lake, it would relieve some of the operational pressure managers face to release water due to flood concerns or meeting environmental regulations.
The location for Alder Reservoir is also intriguing from an engineering perspective.
Kenneth Payne with the El Dorado Water Agency said it is at the convergence of two granite formations with a very deep canyon. This would allow cold water to be stored in a deep and narrow space with limited evaporation losses. The cold water could also be released to meet environmental concerns for certain fish species downstream.
This cold water component is especially appealing since Folsom is often the first responder to the Delta. Water managers sometimes need to release water from Folsom to help meet environmental water temperature regulations in the Sacramento-San Joaquin Delta. An upstream reservoir like the one at Alder Creek could help offset those cold water needs.
The proposed reservoir water would also be used for the agricultural community of El Dorado County. If needed, the water could also help cities like Folsom, Roseville and the San Juan Water District that currently rely on water from Folsom Lake.
When released, the water would move through creeks, streams, rivers and even the old gold mining flume system. In fact, this reservoir has been on the books since 1916.
Payne said it was during that time the county was seeing tremendous agricultural growth. There was a need to figure out water supply, so people started to look at ways to store rainfall and snowmelt. A total of 16 sites were proposed, but the only one still being considered is near Alder Creek.
The next steps for moving this forward are starting the feasibility study and economic analysis. Funding would come from local, state and federal agencies at a cost of about $1.4 billion and take about 10 to 15 years to complete.