WASHINGTON RESERVOIR REPORT

Last Updated: January 6, 2026

Washington's dams and reservoirs are integral to the state's water management, providing essential resources for irrigation, power generation, and flood control. A recent analysis of data reveals varying conditions across key reservoirs, with some experiencing abnormal levels for this time of year. Wynoochee Lake near Grisdale, Lake Tapps near Sumner, and Diablo Reservoir near Newhalem are holding close to their average storage levels, with Wynoochee and Lake Tapps slightly below at 774 feet and 538 feet, respectively, and Diablo at an even 1201 feet. These figures are generally in line with historical averages for early January, indicating typical water management operations.

In contrast, Mud Mountain Lake near Buckley and Franklin Roosevelt Lake at Grand Coulee Dam are reporting higher than average water levels, with Mud Mountain at 1091 feet, significantly above its average of 931.23 feet, and Roosevelt Lake at 1284 feet, above its average of 1275.62 feet. This could be related to recent severe weather events, as outlined in a USACE-managed flood response and reports of December's atmospheric river soaking the region. Such weather patterns can enhance snowpack and river flows, impacting reservoir levels. However, the presence of abnormally high or low water levels may also be symptomatic of broader challenges in water management and aging infrastructure, as discussed by experts highlighting concerns over America's flood defenses and environmental pressures on water resources. The Lake Scanewa near Kosmos is currently not reporting an updated water level, which is an anomaly that requires further investigation to ascertain the condition of this reservoir. It is essential for water managers and policymakers to monitor these variations closely and to understand the contributing factors, including the potential influence of variable precipitation patterns and the need for vigilant infrastructure maintenance and upgrades.

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.