Water Supply

The Sierra Nevada Region plays a critical role in California’s water system. More than 60 percent of California’s developed water supply originates in the Region. Snowpack in the Region is a critical form of water storage, and Sierra forests and meadows play important roles in ensuring water quality and reliability. Further, 75 percent of the fresh water that flows into the Sacramento-San Joaquin Delta comes from the Sierra. The Delta is the hub of the state of California’s water system, providing water to more than 25 million Californians and three million acres of agricultural land. Together, these two regions act as California’s natural water infrastructure, the foundation of a complex system that provides clean, reliable water for the state.

The quantity and quality of water from Sierra Nevada headwaters is threatened by overcrowded forests, degraded meadows, and a changing climate. Historically, Sierra forests and meadows yielded more water, of a higher quality, and later in the summer than they do today. Although changing weather patterns play an important role, less crowded forests consumed less water per acre and allowed a deeper snowpack to develop. Meadows characterized by meandering streams and floodplains acted like sponges, soaking up snowmelt, filtering it, and releasing it slowly—extending runoff into the dry California summer. Today, Sierra forests have grown more dense and many meadow floodplains are channelized. As a result, our Sierra headwaters are less capable of providing these beneficial services to the state water system.

Overcrowded forests also threaten our water supply infrastructure. They are less resilient to drought, beetle infestation, and wildfire. The result is unprecedented tree mortality in the Sierra Nevada—129 million killed by beetles and drought alone since 2010. Forests of dead trees create numerous challenges for water management, from an increase in flooding and landslides to a reduction in water quality and reservoir capacity.

Highlights From Our Newsroom

View our most recent articles about water supply in the Sierra Nevada.

Regional Challenges, State Priorities

Sierra Nevada forests are unhealthy, vulnerable to damaging wildfires and an accelerating climate crisis. Local communities and economies are at risk. And it’s not just the Sierra Nevada, California’s water security, outdoor access, biodiversity, and climate leadership all depend upon healthy, resilient Sierra forests.

Learn more about these challenges and priorities: