According to the U.S. Army Corps of Engineers, a dry winter and early spring has produced less than optimal water conditions throughout the Willamette Valley Project.
So, what does this mean for Detroit Lake?
“A better forecast right now means we’re seeing inflows higher than we previously forecast, about a few weeks ago,” said Lauren Bennett, public affairs specialist for the Portland district. “May has brought a lot of precipitation to the Valley, which is great to help us try to get to the rule curve – the congressionally-authorized maximum water level we can be at on a given day – and have our reservoirs be as full as possible as we head into ‘conservation season’ where we reduce our flows to store water in the reservoirs for recreation.”
Bennett said the Corps has been working with its partners, including the National Marine Fisheries Service and the Oregon Department of Fish and Wildlife to reduce downstream releases. Their objective is to keep back as much water as possible across the Willamette Valley’s 13 dams and reservoirs, which are primarily a rain-driven system.
Basin-wide, reservoirs are currently 80 percent full, according to Corps information released on May 15.
“It’s important to note that inflows are better right now because snow melt has largely melted off,” Bennett said. “Melted snow from high elevations generally sustains inflows into our reservoirs later in the summer months and helps us keep our reservoirs full in the late summer because of this. However, we have had a pretty dry winter and spring, and above-average warm temperatures this spring have melted off a lot of the snow that would usually help fill reservoirs later in the summer. So, while this is good for the ‘now,’ it’s not great for ‘later’ refill.”
In a recent online presentation, Erik Peterson, operations project manager, spoke about the COVID-19 response to continuity in the Willamette Valley. He talked about supporting the emergency and operating facilities by moving water and making power while taking care of people.
Other topics included: monitoring facilities; accomplishing high priority work; complying with the Endangered Species Act; and resource protections.
Current conditions in the Willamette Basin embrace that the Detroit spillway gate construction did not impact refill of the lake, which is at 90% of capacity.
“We’re already back to where we anticipated we should be at the time we began refill in February,” he said.
Following a lean winter of precipitation but with a bump in rain in May, Detroit is “pretty close to full” and should remain there throughout the summer season, Peterson predicted.
Along with eight other Oregon state parks, Detroit Lake reopened May 5, with social distancing requirements in place. Although boating is on again, several popular events have been postponed due to COVID-19 restrictions, including the Detroit Lake Fishing Derby. Pending is the popular Fireworks Over the Lake Fourth of July celebration along with the fireworks fundraiser, BBQ & Brews, held on the Friday prior to the fireworks. Also pending are the annual Cruz-in at the Lake and possibly the waterski show if expected water levels hold.
The National Oceanic and Atmosphere Administration forecast for June a below-normal water supply and higher than average temperatures throughout Oregon. Along with the lack of precipitation received so far this year, as well as early snow-melt runoff due to warmer temperatures, this forecast is setting the stage for “abnormally dry” to “moderately drought” conditions to continue through summer, according to the Corps.
“Every water year is different,” he said. “And forecasting has limitations.”
Based on current conditions and forecasts, the Corps is working collaboratively with federal, state and local agencies to plan water management operations that will optimize water resources.
“Adaptive management has improved system storage projections,” Peterson said. “That’s a really good thing. Also, timely precipitation and some snow melt runoff is improving the forecast.”
Peterson said some Willamette Valley basins will be more impacted than others.
“Flow targets are under constant assessment,” he said. “We’ll continue to manage that through the course of the season. Our intent to communicate as forecast and flow conditions change.”
The Corps hosted three virtual information sessions on water conditions, forecasts and management in early May. These recorded meetings can be viewed here: www.youtube.com/PortlandCorps/videos.
