The Bureau of Reclamation has begun constructing an emergency water intake system with barges and water pumps in case the water level in Folsom Reservoir falls below water intakes that supply drinking water to surrounding cities.
The bureau is juggling water releases in its system of reservoirs and must release water from Folsom to fight delta salinity levels.
It is saving water at Shasta and Oroville reservoirs for use later in the season to help spawning salmon populations.
But that means water levels may get down to 12 percent of capacity, a historic low that could be reached by the fall. Water flowing through the underwater intakes goes to Folsom, Granite Bay, Roseville, Citrus Heights, Fair Oaks and Orangevale.
The water level has been dropping about 3 feet every four days or so and is about 45 feet above the intakes now.
Bureau officials believe they can manage releases so the intakes won't be at risk of going high and dry, but the $3.5 million project is a necessary back-up as winter approaches.
"Hopefully conditions will change, and we'll get the rain and the snow that we need to operate the system continually without the barges," said Bureau of Reclamation Spokesperson Louis Moore.
The barges will be built near the dam by contractors and be placed in the lake just south of the dam. Pipes running from the barges will run on top of the dam into the water distribution system.
In the meantime, some of the communities affected are searching for additional sources of water including using their own emergency underground wells.