Federal regulators are again delving into the process of dividing up roughly 1.6 million acre-feet of water stored behind 13 dams in Oregon’s Willamette Valley.
Those dams perform flood control during the rainy winter months but also hold water during the spring and summer that’s designated for joint use by irrigators, municipalities, industries, recreationists and fish.
Exactly how much water is allocated for each use is currently undefined, but the U.S. Army Corps of Engineers — which operates the dams — is under an internal deadline to ration it out by mid-2017.
The agency recently restarted the earliest “scoping” phase of the allocation process, which involves collecting information from the public on water needs.
Future irrigation demands calculated by the Oregon Water Resources Department and Oregon Department of Agriculture will be considered by the Corps.
The process of allocating the water was previously undertaken in the 1990s but was postponed by a “biological opinion” that analyzed the impact of dams on several fish protected under the Endangered Species Act, said Mary Anne Nash, public policy counsel for the Oregon Farm Bureau.
“It halted the process while they did that work,” she said.
Under a biological opinion completed in 2008, the amount of water slated for irrigation is capped at 95,000 acre feet, but the Oregon Farm Bureau and other irrigator groups hope to increase agriculture’s share under the Army Corps’ allocation process.
Currently, irrigators in the Willamette Valley have contracted with the federal government to use 74,000 acre-feet of the water available.
It’s too early to tell how much water will realistically be devoted to irrigation under the allocation plan, which is expected to be submitted for approval by Congress in 2018, said Nash.
Apart from the water supply, growers must have the facilities to convey it to their crops, she said. “That’s been a missing piece for quite a while.”
Due to the expense involved, such infrastructure has largely been built near the river systems on which the dams are located, Nash said. The longer-term goal is to irrigate farmland that’s further away from those sources.
Drought conditions like those in 2015 may increase irrigation demands in future years. More farmers in the region are also growing higher-value crops, such as blueberries, that require summer irrigation.
Greg Bennett, an onion farmer near Salem, Ore., said the Willamette Valley may have an opportunity to increase vegetable production as California farmers continue to face water scarcity.
“I’m really hoping we can realize the value of what we have,” he said.
While the 13 dams have the capacity to store 1.6 million acre-feet, that represents ideal water conditions, said Kathryn Warner, an environmental scientist at the Corps.
Realistically, the dams hold about 1.4 million acre feet of water during an adequate year, and 500,000 acre-feet are dedicated to in-stream uses for fish under the current biological opinion.
The amount designated to irrigation could rise above 95,000 acre feet, but the entire allocation plan must be reviewed under the National Environmental Policy Act, Warner said.
This process will include inter-agency consultation on species impacts and may require another biological opinion, Warner said.