Posted on July 29, 2026
PORTLAND, Ore. – This summer, visitors to and residents near Detroit Reservoir are noticing lower-than-average water levels.
Because of active public interest regarding the U.S. Army Corps of Engineers (USACE) Portland District’s operations at Detroit Reservoir – including this fall’s reservoir drawdown for fish passage – the agency is providing answers to the five most common questions.
1. The Detroit Reservoir is low – has the drawdown already started?
No. The Detroit deep drawdown will start after Nov. 1, 2026. USACE will use forecast data to identify ideal conditions to start the drawdown any time after Nov. 1 but before Dec. 31.
Current lower than average water levels are due to seasonal drought. More info on reservoir levels during the drought can be found here.
2. Is the 2026 Detroit Reservoir drawdown the lowest level the reservoir has ever reached?
No. In 2026, USACE will draw Detroit Reservoir down to an elevation of 1425 ft, an elevation the reservoir has previously reached in 2015 and 2019.
3. Will the 2026 Detroit Reservoir drawdown affect drinking water?
Drinking water is not expected to be impacted: The reservoir has previously reached an elevation of 1425 feet (in 2015 and 2019) without reported impacts to drinking water.
4. Will future, deeper drawdowns at Detroit Reservoir affect drinking water?
USACE continues to develop an Emergency Response and Communication Plans with the state and drinking water facilities, which will identify conditions for modifying, pausing, or stopping the drawdown.
For reference, in 2024, USACE halted to the Green Peter drawdown due to risks posed to their water treatment facilities.
5. How long will the drawdown last?
It may take up to two weeks to draw the reservoir down to the target elevation of 1425 feet. USACE will then hold that elevation for two weeks unless a major storm event occurs.
This plan gives the reservoir two months to refill to normal levels during the rainy season, which can happen as quickly as few days.
BACKGROUND
In late December 2024, the National Marine Fisheries Service published a Biological Opinion with a deeper fall drawdown at Detroit Reservoir to support the protection of endangered fish species.
USACE is taking a careful, “step down” approach to the Detroit drawdown to reduce turbidity that could impact local water systems and downstream river health:
- Incremental approach: The first year of the drawdown in 2026, USACE will lower the reservoir to 1,425 feet – a level reached safely in past without causing muddy water (turbidity) issues downstream. In following years, USACE will gradually lower the reservoir to 1395 feet – the target for safe fish passage through an outlet in the dam.
- Real-time management: USACE will monitor water quality in real-time. If measurements show that turbid water is moving downstream and is likely to impact local drinking water systems, we will communicate with drinking water facilities and the State about whether to pause, modify, or stop the drawdown.
Detroit Reservoir is one of 13 dams USACE maintains and operates in the Willamette River Basin. These dams provide flood risk management, water for irrigation and communities, recreation opportunities, in addition to supporting fish and wildlife. Managing these dams is a complex task that requires balancing a variety of needs and interests. Through the flood risk management mission, the Willamette Valley System of reservoirs and dams prevents millions of dollars in flood damages each year.
