Girding for drought at the locks; needs of boaters, fish, lakes all in play

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As the region flirts with drought, managers of the Ballard Locks are taking steps to strike a delicate balance among the needs of fish, boaters and the environment.

For a start, the Army Corps of Engineers, which operates the 84-year-old locks, is tanking up Lake Washington ahead of schedule to ensure adequate flows for fish in the spring. And it is laying plans for further action -- such as opening the locks less frequently for boaters -- in case the drought that water managers dread materializes later this year.

Operating the locks requires a complex management of the freshwater that flows into Lake Washington and Lake Union from the Cedar River, and of the saltwater that infiltrates the Ship Canal through the locks.

Providing adequate water for salmon in the Cedar River; keeping saltwater out of the freshwater lakes; and providing safe migration for salmon through the locks is all at stake.

And the job is trickier in a low water year.

Water levels in Lake Washington must be kept at no lower than 20 feet above sea level. In a low-water year, that can require a range of special operations of the locks, including opening the locks less frequently - resulting in long waits for boaters.

In 1992, the region's last dry spell, there were restrictions on opening the locks from June 8 through Sept. 1 to save freshwater spilled from the lakes and to reduce saltwater infiltration from Puget Sound.

Boaters faced waits of 45 minutes and longer, instead of cruising through on demand as they usually do.

It's too early to say if anything like that will be required this year. But the Corps of Engineers will be meeting soon to assess water needs for the spring and craft an action plan in case the summer brings drought.

"It's been so dry, the forecasts have been a bust, and we are concerned about it," said David Van Rijn, biologist for the Corps of Engineers' Seattle District.

"We want to get together and talk about what we do if it's still a really pathetic dry year in May and June."

The corps has a four-stage conservation protocol in low-water years that enables it to manage the competing needs of fish, navigation and the environment.

In a Stage One situation, the least severe, managers would fill Lake Washington to 22 feet above sea level, to bank water in case of lack of rain.

Managers may curtail operation of a drain at the bottom of the locks used to disperse saltwater and keep it from entering Salmon Bay, just east of the locks.

Saltwater enters the Ship Canal in a wedge-shaped plume, which managers control in part by opening the gravity-operated drain. It pulls the heavier saltwater back out to Shilshole Bay.

But quantities of freshwater flow through the drain as well, so closing the drain helps maintain higher freshwater levels in lakes Washington and Union.

Biologists don't want saltwater in the lakes because they are concerned it will form a heavier layer at the bottom of the much-deeper Lake Washington that will not disperse. That would destroy its freshwater ecosystems.

In a Stage Two situation, managers issue a news release informing boaters they may face delays at the locks, perhaps five to 10 minutes, until another boat shows up to make operating the lock more efficient.

The locks operate seven days a week, moving an estimated 75,000 vessels a year and more than 2 million tons of commercial cargo between Puget Sound and Lake Union and Lake Washington.

In a Stage Three situation, managers tell boaters they will definitely face delays. Lock managers also request a waiver from the state Department of Ecology on salinity standards in the Ship Canal.

Water flows at the fish ladder are also reduced intermittently, especially at night, when fewer fish migrate.

In a Stage Four situation, commercial and recreational boaters are warned of significant delays at the locks, of an hour or more. Flows at the fish ladder are closed intermittently.

The corps also asks Seattle Public Utilities, which regulates flow from the Cedar River, to allow higher flows into Lake Washington.

Seattle Public Utilities is expecting low flows in the Cedar this year because of low snowpack. The snowpack season is three-quarters finished, but snowpack is way behind, about 65 percent of normal in the Cedar Basin, according to George Schneider, water-resource manager at Seattle Public Utilities.

The weather from here on out will determine if conservation is necessary to protect chinook, sockeye, steelhead and coho in the Cedar River and bull trout in the Cedar reservoir.

If March, April and May see normal precipitation, the reservoir, now 3 to 4 feet below where it would normally be, should refill easily. That water will be important later, to maintain flows in the Cedar as well as water levels in Lake Washington.

Filling Lake Washington now will help juvenile chinook salmon get out to the Sound come spring. The fish travel through flumes specially installed in locks, as well as through the locks themselves.

Puget Sound Chinook are protected as a threatened species under the federal Endangered Species Act.

The extended forecast calls for slightly above-average precipitation over the next three months. But long-range forecasts are notoriously unreliable. And the wettest months of the year are already past. Precipitation has been 50 to 65 percent of average so far for the water year, which began Oct. 1.

This has been the driest water year since 1976-77, and some predict it could end up even drier.

"We've gone through the wettest part of the year and we just haven't gotten the weather we normally would, that's our main concern," said Tom Murphy, meteorologist for the corps. "So we are taking precautionary steps, and monitoring water use very carefully."

Lynda V. Mapes can be reached at 206-464-2736 or lmapes@seattletimes.com.