Mirky Future For Delightful Delta On River Walla Walla Bird Area Imperiled By Evolution

The Walla Walla River’s delta is like a giant kidney, filtering sediments and other impurities.

Mike Denny worries that those kidneys are infected. They are definitely swelling and may ultimately fail.

Few people know the delta as intimately as Denny, a Walla Walla area bird watcher. He has visited the area area around the U.S. Army Corps of Engineers’ Madame Dorian Park regularly since 1979 to take part in a local shorebird census.

The delta is not natural. It was created when the waters behind McNary Dam flooded the mouth of the Walla Walla River in 1953, backing 7.5 miles upstream from the river’s former mouth, according to a 1998 thesis paper written by former Whitman College geology-environmental studies student Heidi Van Auken.

When the Walla Walla hits the dammed-up slackwater, the water slows and drops the sediments it used to carry into the Columbia. By the early 1970s, this process had filled the swampy lowlands along the Walla Walla’s old banks and had started pushing the delta into the Columbia, according to Van Auken.

This artificial estuary has proven to be an important Eastern Washington habitat for migrating birds. Large flocks of many species winter here. Washington’s only breeding colony of white pelicans feeds here, as do rare birds like the Hudsonian godwit.

One morning in August, Denny recorded 80 western sandpipers, three semipalmated plovers, three longbilled dowitchers and 14 killdeers.

“The silt here has created tremendous wildlife habitat,” Denny said, standing in knee-deep murky water near the Walla Walla’s mouth.

“The wildlife here (has) a haven. There’s nothing else like this in Eastern Washington.”

Few such places are found anywhere between the Cascades and the Rockies, said Mark Halupczok, a wildlife biologist who manages the park property for the corps.

“It’s one of the few stopovers,” Halupczok said. “You go south of here and there’s not a whole lot of habitat like this left.”

The National Audubon Society recently designated the delta an “Important Bird Area,” a distinction given to just a few others in southeastern Washington.

But all is not well.

Purple loosestrife is a pretty plant that’s considered a noxious weed. It crowds out the native cattails, which provide cover and food for fish and birds along the river’s edge. Likewise, false indigo and yellow star thistle are suffocating the native willows.

Controlling noxious weeds isn’t easy, Denny said. Expensive chemical treatments would be required to kill the weeds without harming the native plants.

And the changes in the river that caused the delta - the slack water from the Columbia - have been a mixed blessing for fish.

On the one hand, Halupczok said, at least there is water here - unlike stretches above Nine Mile Canyon - to support one of the few public fisheries left on the Walla Walla.

The fishing can be good. Andre Hendrix, a Pasco man fishing the upper end of the park, said, “I’ve hardly ever come out here and not caught a fish.”

The water is muddy, slow-moving and warm. Migrating steelhead pass through in the spring, but the rest of the year, it is more suited for bass and catfish that have migrated into the river’s mouth.

The delta is growing, Denny said. It has doubled in the almost 20 years he has been visiting. The biggest, most recent growth was the result of the 1996 and 1997 floods. They wreaked havoc across farmland upriver, but dropped most of that soil here. Plants are taking hold in that freshly dumped soil, Halupczok said. It is becoming permanent.

Denny worries the delta will one day stretch so far into the Columbia that it will block barge shipping and will have to be dredged up. That could result in more water draining out of the lower river wetlands - reducing their value as bird habitat.

Eventually big cottonwoods will grow on the new delta banks, altering the course of the river in natural - not man-made - ways.

“This is part of the whole cycle,” he said.