CALIFORNIA RESERVOIR REPORT

Last Updated: December 23, 2025

California's network of dams and reservoirs is experiencing a mix of conditions, with significant fluctuations in water storage levels due to recent weather patterns. A notable increase in precipitation, including heavy rainfall and atmospheric rivers, has led to a surge in water levels at many reservoirs, such as Lake Oroville, which saw an over 6-foot rise in a single day. However, despite the influx of water, some reservoirs remain below their historical averages, pointing to the ongoing challenges posed by prolonged drought conditions and water management disputes, especially concerning the Colorado River basin, where states struggle to reach an agreement on water sharing.

Major dams like San Vicente are coping with higher than average storage levels, reflecting the impact of the recent storms. Conversely, dams such as Cherry Valley have reported negative storage changes, indicating potential structural or reporting issues. These abnormal conditions are influenced by factors like snowpack levels, river flows, and the region's complex water rights debates. The state's water infrastructure is currently under stress from the immediate impacts of flooding and longer-term concerns over water supply sustainability. Coordination among interstate river basins, such as the Colorado River, remains critical to address the fluctuating water landscape, ensuring power generation, and securing water supplies for diverse needs across California.

California has over 1,400 reservoirs and dams, which provide water for agriculture, industry, and households. Some of the major reservoirs in the state include Lake Oroville, Shasta Lake, and San Luis Reservoir. These reservoirs are fed by streams, rivers, and creeks such as the Feather River, Sacramento River, and San Joaquin River. The snowpack in the Sierra Nevada mountains is a crucial source of water for these reservoirs, as it melts during the spring and summer and fills the streams and rivers that flow into the reservoirs. However, drought conditions have been a major concern in recent years, with record low levels in some reservoirs. Seasonal trends show that reservoirs are typically at their lowest levels in the fall and winter, and reach their highest levels in the spring and summer. Overall, California’s reservoirs and dams play a vital role in managing the state’s water resources and ensuring a reliable water supply for its residents.

California has over 1,400 reservoirs and dams, which provide water for agriculture, industry, and households. Some of the major reservoirs in the state include Lake Oroville, Shasta Lake, and San Luis Reservoir. These reservoirs are fed by streams, rivers, and creeks such as the Feather River, Sacramento River, and San Joaquin River. The snowpack in the Sierra Nevada mountains is a crucial source of water for these reservoirs, as it melts during the spring and summer and fills the streams and rivers that flow into the reservoirs. However, drought conditions have been a major concern in recent years, with record low levels in some reservoirs. Seasonal trends show that reservoirs are typically at their lowest levels in the fall and winter, and reach their highest levels in the spring and summer. Overall, California’s reservoirs and dams play a vital role in managing the state’s water resources and ensuring a reliable water supply for its residents.