The U.S. Department of the Interior's Bureau of Reclamation released the American River Basin Study Aug. 31.
The study found the basin in central California will see increasing temperatures and a declining snowpack through the end of the 21st century, according to a news release. In addition, the study also found an increase in the variation of fall and winter precipitation, which will amplify the severity of droughts and flooding in the basin.
"Water management in the basin is expected to be more challenging in the future due to climate pressures that include warming temperatures, shrinking snowpack, shorter and more intense wet seasons and rising sea levels," California-Great Basin Regional Director Ernest Conant said in the release. "We are excited for the partnerships and collaboration within the basin and look forward to working with them on the identified adaptation portfolios to address the vulnerabilities and maintain a balance between supply and demand in the basin."
The report's areas of study include: the American River watershed, covering more than 2,000 square miles from the Sacramento River to the northern Sierra Nevada mountains west of Lake Tahoe; the ARBS Non-Federal Partners' Service Areas Outside of the American River Watershed, representing areas outside of the American River Watershed in adjacent watersheds of the Bear River and Cosumnes River served by the Non-Federal Partners with American River water; and the North and South American Groundwater Basins, separated by the American River in the west side of the study area, their eastern boundary representing the approximate edge of the alluvial basin where little or no groundwater flows into or out of the Sierra Nevada basement rock basins, according to the study.
Although the study found no clear precipitation projection trends over the current century, it did say that surface are expected to continue increasing, the study reported. Summer temperatures could rise 7.2 degrees Fahrenheit by the end of the century, with winter temperatures decreasing by 4.9 degrees Fahrenheit.
Adaptation strategies in the basin are already progressing to increase agricultural and urban water use efficiency, water transfers and exchanges within the basin and improving headwaters and forest health, according to the news release. New strategy portfolios were developed by Reclamation and collaborators for further elaboration, as well as to better manage supply and demand. One such portfolio emphasizes the importance of long-term Central Valley Project contracts for regional reliability.
According to the release, other adaption portfolios will evaluate the use of high elevation, off-stream storage to replace to replace lost storage from reduced snowpack and earlier snowmelt; the utilization of preexisting diversion facilities on the Sacramento River and the exchange water supply to reduce the strain on Folsom Reservoir and the American River; the raise of Folsom Dam and other upstream flood control space through facility modifications meant to increase flood control space; releasing flood waters earlier than usual to recharge groundwater and create additional regional water supply and ecosystem benefits; and the effectiveness of the flow management standard for the Lower American River in the 2015 update of the Sacramento Water Forum Agreement to reduce the effects of climate change on the river's ecosystem and fisheries.
