Study-related lake levels may benefit more than fish

Scott Swanson

The U.S. Army Corps of Engineers’ efforts to improve life for young steelhead and salmon moving down the South Santiam River may be a boon for Foster Lake recreational users this summer.

That’s because the Corps raised Foster’s water level to nearly full pool – roughly 635 feet – earlier this month as part of a year-long study that will help officials determine how to better operate Foster Dam to improve the survival of spring Chinook, winter steelhead and other fish species in the South Santiam River Basin. The study will collect information about fish behavior, density and movement in the reservoir, and fish passage through the dam.

Last week the Corps announced that its reservoir regulators think it’s unlikely that water levels at most of the Corps’ 13 reservoirs in the Willamette Basin will rise much beyond current levels – 3 to 28 feet below their target elevations – without significant additional rain.

“Maintaining water levels high enough for late summer recreation may also be a challenge,” the Corps said in a statement.

County Parks and Recreation Director Brian Carroll said the water in Foster was raised earlier than parks staff expected – usually it doesn’t happen until just before Memorial Day weekend – and although the lake is about 2 feet lower than it usually is during the summer, it looks like it will work for the county’s recreational needs.

He said county staff measured the water level after the lake was raised and found that most boat slips at moorages at Foster were surrounded by at least 3 feet of water.

“The indications were that the lower water level may not have impacted the boat ramps as much as it could have,” he said. “If this fish passage experiment works, in the long run it could be really good for Foster. We won’t have to worry in the future about potential drawdowns. We may see a much more stable reservoir.”

At Green Peter, however, the water level was at 995 feet above sea level on Monday, about 14 feet below full pool and Corps spokesman Scott Clemans said it remains to be seen how much water will be in the lake this summer. Water from the lake is essential to maintaining required water flows and temperatures in the Santiam tributaries and the Willamette River, he said.

The Corps started refilling its 13 Willamette Valley Project reservoirs in February for the summer water conservation season. The Natural Resource Conservation Service reports that total precipitation for the Willamette Basin was only about 60 percent of average for February and March, then average for April. The basin’s snowpack has also been melting off faster than average.

“We responded to the low water supply by minimizing flows from most of our reservoirs in February and March to maximize refill potential,” said Erik Petersen, Willamette Valley Project operations manager. “However, we needed to increase flows again in April and May.”

The Corps is required to meet minimum flow targets on the mainstem Willamette River and many of its tributaries to support water quality and the lifecycles of endangered spring Chinook salmon and winter steelhead. Without the additional water from Corps reservoirs, Petersen estimates the Willamette at Salem would have been almost a third below target in April and May.

The combination of lower than average water supplies and higher releases for fish early in the conservation season may make it difficult to maintain adequate lake levels for late season recreation at other Corps reservoirs.

“It’s obviously still a long ways off and there are many factors that could change, but our latest forecast indicates water levels at the end of August may be near the bottom of some popular boat ramps and marinas,” Petersen said.

Clemans said the current estimate, barring substantial rainfall, is that Green Peter will not rise above 1005 feet.

“Green Peter is one of the reservoirs that we do rely on in early summer to provide the extra water needed to keep flows at required minimums,” he said.

Clemans said the water levels at most of the Corps reservoirs are about 15 percent below where operators would like them to be.

“It’s not that the reservoirs are in too bad of shape,” he said, adding that the Corps tries to hold water in its larger reservoirs, such as Detroit or Lookout Point, for timed releases to maintain flows and temperatures for endangered species later in the summer.

“It’s not that we don’t have big buckets of water to use, but we have to use some buckets of water for temperature control” best suited to the needs of endangered fish.

For many years the Corps has conducted a special operation at Foster Dam in April and May in which reservoir regulators hold the water level between 613 and 616 feet, allowing the surface water where juvenile steelhead usually swim to gently spill through a weir installed in one of the dam’s spillway bays. Oregon Department of Fish and Wildlife research into the timing of the runs has shown that many juvenile fish actually leave the lake later in the summer, which is why the study is being conducted.

Clemans said it will probably be next fall before researchers have any substantive data.

“We’re still pretty early,” he said, noting that the study is expected to continue into the fall. “We probably won’t have good feedback for a while.”

Carroll said that if researchers are right, and the weir program is redesigned, the lake level will be up longer, giving boaters more surface area and providing more time for county staff to clean up debris from winter storms.

“There are so many potential benefits if this works,” he said.

The Corps is encouraging boaters and other reservoir users to closely monitor current and expected future water levels when making their summer recreation plans.

Current Willamette Valley reservoir and boat ramp levels are available from Portland District at Three-day forecasts and 10-day trends are available from the Northwest River Forecast Center at