WASHINGTON RESERVOIR REPORT

Last Updated: December 20, 2025

Washington's dams and reservoirs exhibit a mix of conditions, some in line with seasonal expectations and others showing signs of abnormal levels. Among the notable measurements, Mud Mountain Lake near Buckley stands out with a current water surface elevation of 1160 feet, significantly higher than its average of 930.68 feet, indicating potential overflow risks. Conversely, Wynoochee Lake near Grisdale is below its average, with a current elevation of 774 feet compared to its typical 776.34 feet. Most other reservoirs, including Lake Tapps and Diablo Reservoir, are hovering around their average levels. However, Lake Shannon at Concrete shows an elevation increase to 441 feet from its average of 420.51 feet, suggesting higher inflow rates, possibly due to recent weather patterns. The dataset's last observations were recorded on December 20, 2025.

The abnormal reservoir conditions in certain areas of Washington could be attributed to recent climate events. Reports indicate that the state experienced the warmest fall on record, which may have affected snowpack levels and subsequently river flows. Additionally, atmospheric rivers have brought extensive rainfall to the West, potentially impacting reservoir levels through increased runoff and inflow. The situation is further complicated by a corresponding need for flood management, with state funding directed towards flood victims. These water level variabilities at major dams and reservoirs like Mud Mountain Lake and Lake Shannon are critical to monitor as they can influence flood risk, water supply, and ecosystem health. It's essential to cross-reference these observed data with meteorological reports and water management policies to ensure accurate assessments and appropriate responses to these fluctuating conditions.

Washington state has over 700 dams and reservoirs, many of which provide hydroelectric power and irrigation for agriculture. The Columbia River is the largest source of water for the state, with many major reservoirs located along its length. These include Grand Coulee, Banks Lake, and Lake Roosevelt. The Yakima River basin also has several important reservoirs, including Cle Elum Lake, Kachess Lake, and Bumping Lake. Snowpack in the Cascades and Olympics is critical for water supply, particularly for irrigation during the dry summer months. In recent years, drought conditions have affected much of the state, with record low snowpack levels in 2015 leading to restrictions on water use. Seasonal trends generally see peak water levels in the spring as snowmelt increases streamflow, followed by a gradual decline throughout the summer and fall. Overall, the hydrology of Washington is complex, with a mix of natural and human factors affecting the availability and use of water resources.

Washington state has over 700 dams and reservoirs, many of which provide hydroelectric power and irrigation for agriculture. The Columbia River is the largest source of water for the state, with many major reservoirs located along its length. These include Grand Coulee, Banks Lake, and Lake Roosevelt. The Yakima River basin also has several important reservoirs, including Cle Elum Lake, Kachess Lake, and Bumping Lake. Snowpack in the Cascades and Olympics is critical for water supply, particularly for irrigation during the dry summer months. In recent years, drought conditions have affected much of the state, with record low snowpack levels in 2015 leading to restrictions on water use. Seasonal trends generally see peak water levels in the spring as snowmelt increases streamflow, followed by a gradual decline throughout the summer and fall. Overall, the hydrology of Washington is complex, with a mix of natural and human factors affecting the availability and use of water resources.