What's behind flooding on the Upper Deschutes?

September 18, 2017
What's behind flooding on the Upper Deschutes?

Warm weather, water management, plant life all named as culprits

SUNRIVER — Water levels along the Upper Deschutes River have slowly receded over the first couple weeks of September, which means life is finally returning to normal for Nancy Capell and her garden.

Capell, 65, saw water from the Deschutes River rise up over its normal banks into the backyard of her home in the Three Rivers subdivision in July, flooding her grass and drowning many of the pea and potato plants in her enclosed garden.

The rising water transformed her yard, and others on her street, into a water wonderland, complete with geese, great blue herons and kayaking neighbors.

“We couldn’t use it for two months,” she said Thursday. “But we did have our own lake.”

While the water volume during the summer was not record-setting, the experiences of property owners like Capell underscore some of the problems along the Upper Deschutes caused by flows that vary dramatically between winter and summer months.

“It’s a fantastic river of the West. Living on it is an honor and a privilege,” Capell said. “I just think it isn’t healthy for the river.”

While Capell said the flooding was far worse than during her two previous summers in the neighborhood, the raw stream flow totals upriver were not much higher than usual. During July and August, the river tends to flow at up to 1,600 cubic feet per second at the gauge downriver of Wickiup Reservoir, and at up 2,100 cubic feet per second near Benham Falls, according to data from the Oregon Water Resources Department.

While the flow stayed at 1,600 cfs for longer than it had during many recent years, it was not measurably higher at its peak, according to the department’s data.

Tod Heisler, executive director of the Deschutes River Conservancy, a nonprofit group that focuses on restoring stream flow in the Des­chutes Basin, emphasized that flooding along the river was due to a variety of factors, ranging from summer temperatures to ongoing litigation on the river.

“This is highly variable,” he said. “It has been a problem in the past, and it will likely be a problem in the future.”

Flows on the Deschutes are low during the winter and spring, when much of the water gets retained in large reservoirs, according to Mathias Perle, project manager for the Upper Deschutes Watershed Council, a nonprofit that handles habitat restoration in the Deschutes Basin.

However, water levels along the Upper Deschutes River rise during the summer every year like clockwork, a consequence of farmers and other customers of Central Oregon’s irrigation districts needing water from the reservoirs as the weather gets hotter and drier. As that water is released, the river rises.

Kyle Gorman, south central region manager for the Oregon Water Resources Department, added that hot, dry summers tend to result in the diversion of more water to irrigation canals. Bend had its warmest August on record this year, while receiving just a trace of rainfall during the month, according to the National Weather Service.

“We had big snow (this winter), but we haven’t had a lot of rain,” Heisler said.

Despite the weather, North Unit Irrigation District, one of eight irrigation districts operating in Central Oregon, has had a relatively normal year for irrigation, according to General Manager Mike Britton. In a typical year, the district, which gets a vast majority of its water from the Des­chutes River, begins diverting water in mid-April and continues into October. Thus far, the year has proceeded according to plan.

Britton pointed to increased vegetation along the river as a reason it might be flooding despite relatively normal water flows. Gorman added that plants can cause the river to slow and spread out, spilling over its banks.

However, Patricia McDowell, professor of geography at University of Oregon and a member of the university’s river research group, said a wetter-than-normal winter wouldn’t be enough to affect the river. Unless there were massive re-vegetation efforts in the affected areas, the impact would likely be small.

The overall effect of the seasonal rise and fall of the river depends on whom you ask. While Britton said he’s heard about the flooding along the Upper Deschutes, living in a floodplain means dealing with occasional floods.

Perle said the ebb and flow can cause problems for the Upper Deschutes’ ecosystem as well. He said fish can get stranded on land and die once the water recedes. Additionally, he said riverbanks can lose vegetation from the cycle of rising and falling water, which contributes to erosion.

“Those banks are pretty raw during the freeze-thaw cycle during the winter,” he said.

Several planning efforts, including a habitat conservation plan from the U.S. Fish and Wildlife Service, are intended to help irrigation districts stay in business, while reducing the change to water flow along the Upper Deschutes. Bridget Moran, head of the Bend field office for the U.S. Fish and Wildlife Service, said the conservation plan is expected to be finalized by 2019.

“I think most people realize we can’t go back to pre-dam, pre-history management of the river,” Perle added. “But we’re trying to find the middle ground.”

— Reporter: 541-617-7818, shamway@bendbulletin.com

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