CALIFORNIA RESERVOIR REPORT

Last Updated: December 25, 2025

California's network of dams and reservoirs is experiencing significant fluctuations in water levels amid a succession of potent atmospheric river storms sweeping across the state. These storms have brought with them heavy rainfall, leading to an increase in reservoir storage and concerns over flash flooding, mudslides, and critical emergency conditions. As per the latest observations dated December 25, 2025, several key reservoirs are reporting above-average storage levels, indicating the impact of relentless precipitation and runoff from surrounding catchment areas.

For example, Lake San Antonio has seen a dramatic rise in storage to 270,863 acre-feet, far surpassing its average of 132,675.92 acre-feet. Similarly, New Melones Reservoir's storage has surged to 1,983,900 acre-feet, well above its average of 1,443,401.24 acre-feet. These increases suggest a robust inflow, likely a result of the saturated watersheds responding to the intense and continuous rainfall. On the other hand, certain reservoirs like Donnells and Hetch Hetchy are reporting diminished storage figures, which may be attributed to operational releases or other management decisions aimed at maintaining safe water levels in anticipation of further rain events. The observed discrepancies in storage levels reflect the complexity of managing water resources in the face of climate variability, with officials balancing flood risks against long-term water supply needs. The ongoing situation underscores the importance of sustained monitoring and adaptive management strategies to safeguard both communities and critical water infrastructure in 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.