After an agreement to stay the Columbia River Basin litigation for up to 10 years, federal water managers will begin spilling more water over basin dams this spring than in past years. In the agreement, the U.S. Army Corps of Engineers (USACE) has committed to spill more water over spillways instead of through turbines during its annual “spring spill” operations at dams on the lower Snake and Columbia rivers as well as expanding spill in the fall and early spring.

“This is an important component of the agreement with Tribes, States, and other parties to implement a long-term, durable path forward,” said Tim Dykstra, USACE’s Northwestern Division Fish Policy lead. “We’ve been using spill as an important tool for fish passage since the mid-1990s to improve migratory conditions for juvenile salmon and steelhead and we will evaluate the impacts of the increased spill to inform our decisions in the future,” he said.

Spill operations targeting juvenile salmon and steelhead generally start April 3 on the lower Snake River and April 10 on the lower Columbia River. USACE uses these operations to decrease the time it takes juvenile salmon and steelhead to move through the system of dams to the Pacific Ocean as well as provide another non-turbine passage route. Many of the dams also have alternative ways to move past the dams.

This year, four projects on the lower Snake River and McNary Dam on the Columbia River will also begin spilling four hours each day through surface passage routes to primarily assist migrating adult steelhead starting March 1. Beginning March 21, those projects, plus John Day Dam on the Columbia River, will begin spilling through surface passage routes 24 hours each day until regular spring spill begins with the goal of providing additional benefits for both juvenile and adult salmon and steelhead.

 “Consistent with our past coordination efforts with regional sovereigns and stakeholders, the Corps looks forward to working closely with our regional partners to ensure implemented operations benefit out-migrating juvenile salmonids, returning adult salmon, steelhead and lamprey as well as resident fish, while simultaneously providing for other important regional needs such as flood risk management, hydropower production, and navigation,” said Dykstra.

Spring spill levels vary at each of the eight dams, but all projects have an upper limit that protects water quality from high levels of total dissolved gas (TDG). Even though this additional water is valuable for fish passage, managers must reduce spill amounts to keep from exceeding 125% TDG limits that state water quality agencies set, and EPA approved in Washington, which adds more intricacy to water management in the basin.

The litigation agreement specifies the following spill operations to benefit salmon and steelhead passage:

• Bonneville, McNary, Ice Harbor, Lower Monumental and Lower Granite dams will spill up to the 125% TDG levels 24 hours per day.
• The Dalles Dam will spill 40% of the river over the spillway.
• John Day Dam will spill 40% of the river over the spillway during the day and up to the 125% TDG levels and at night.
• Little Goose will also spill 16 hours per day up to the 125% TDG levels and reduce spill for eight hours to performance standard spill levels, or 30% of the river. This is to benefit adult fish passage. 

USACE is committed to managing the Columbia River System in a responsible way in accordance with the Congressional authorized purposes of the projects. The new agreement on managing and operating the river system reflects the federal agencies’ shared commitment to collaborating with our Tribal partners, the Northwest states, and others on solutions that achieve the economic and social benefits the Columbia River System while providing for the environmental needs of aquatic resources and wildlife.

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Editor’s note: For b-roll of spring spill from 2023 at Bonneville Dam, visit: