Wickiup Reservoir could reach its highest level in years, but won't fill to the brim

November 6, 2023
Wickiup Reservoir could reach its highest level in years, but won't fill to the brim

Central Oregon remains in a state of drought but reservoir levels have managed to gain ground compared to levels a year ago thanks to a wet spring and conservative water allocations, giving some irrigators a sense of hope that the worst of the low-water years are behind them.

Wickiup Reservoir is currently around 18,000 acre-feet higher than it was this time a year ago. As of Friday, the reservoir was 22% full with five more months to collect water from the area’s springs. Prineville Reservoir, now 59% full and on track to fill up by early May, is also performing well.

“The seeds of drought recovery of the Deschutes River basin are being sown, even if it is a slow process,” said Larry O’Neill, an associate professor in the Oregon State University College of Earth, Ocean and Atmospheric Sciences.

Better storage numbers at Wickiup this year are due in part to some drought recovery in Central Oregon, said O’Neill.

Currently, around 20% of Deschutes County is under severe drought while 66% of the county is under moderate drought. No part of the county is in extreme drought. Those numbers are an improvement compared to the beginning of the year when 56% of the county was under severe drought and 39% in extreme drought.

Wickiup Reservoir levels

Projected reservoir level

Wickiup’s current pace of refill should allow the reservoir to reach around 150,000 acre-feet by the time the irrigation season starts in April, said Mike Britton, executive director of North Unit Irrigation District. That is 75% of capacity, a level not seen since 2018, the last time Wickiup filled to capacity.

An acre-foot of water is 326,000 gallons, or the amount of water needed to cover an acre of land in one foot of water.

Britton adds a caveat that the final number can shift, based on a variety of factors this winter — better-than-average precipitation and snowpack could provide a boost in levels while a hard freeze that disrupts the flow of springs will slow down Wickiup’s rise.

While filling the reservoir is unlikely this winter, a decent amount of snow accumulation and precipitation could bring it close to capacity in 2025.

“A massive snowpack may not fill the reservoir but could provide exceptional natural river flow,” said Britton. “That would minimize the releases of stored water from Wicikup, which, in turn, would allow more storage carryover and more potential to fill Wickiup the following winter.”

Improved starting level

The reservoir’s level is running higher compared to recent years mainly due to its starting position. When the refill began in mid-October it was 12% full, much better than the 3% level a year ago. In 2020 and 2021, the reservoir was drained to its bare bottom with just the Deschutes River flowing through the bed of the reservoir.

While the anticipated fill level this year is a positive sign, Britton adds that the roughly 900 acre-feet flowing into it each day is around 10% lower than average for early November. While the average flow is around 1,000 acre-feet in a day, in very wet years the reservoir can rise 1,250 acre-feet per day at this time of year.

“I’d say the below-average numbers are due to ongoing drought and dry years and the reduced spring and tributary flows into the reservoir,” said Britton.

The reduced spring and tributary flows are connected to an increasingly depleted aquifer under the Deschutes Basin, which has retreated due to several years of drought in Central Oregon. The aquifer feeds water into Wickiup Reservoir from springs, which is fairly unusual as most reservoirs in Oregon fill up from rainwater runoff.

Impacts for North Unit

Wickiup Reservoir is the main source of water for Jefferson County’s North Unit Irrigation District, a center for large-scale commercial farming and a major producer of grass seed and carrot seed. Less water means fewer acres planted, a scenario that has been playing over several years of reduced allocations.

“We are only able to efficiently farm 50 or 60% of our ground with the water allotment we’re getting,” said Richard Macy, a North Unit patron specializing in peppermint, hay, cereals and seed crops. “We are going into the season anticipating short water, but hopefully, it’s better than in the past.”

Macy said farmers have made adjustments, such as scaling up their better-performing crops that offer a higher return while reducing other crops. They are also reducing the overall acres planted but that has inevitable costs.

“It doesn’t take a very sharp pencil to figure out that as you reduce your production, and your fixed costs remain the same but returns on the overall acreage is less, that our profitability is a lot less than it could be or should be,” he said.

Low water allotments can also impact soil quality. Farmers who are unable to regularly rotate crops risk the loss of soil nutrients. Weeds can also take over land that is not watered or given a cover crop.

Cattle ranchers have also been hit hard by the water shortages because it reduces the amount of hay they can grow for their livestock, forcing them to purchase hay from other growers at high costs. Often, the only way to trim expenses is to sell off a portion of their herd.

Britton anticipates that based on current water projections district patrons will get more than the 0.8 acre-feet of water allocation that they received a year ago from Wickiup Reservoir.

Patrons will typically get two acre-feet when the reservoir fills but the current projection is around one acre-foot from Wickiup Reservoir, he said. The district will remain conservative in its water allocation so that more water can be left in Wickiup at the end of the season to increase its banked water reserve.

“If we have a tremendous winter, it would potentially leave more water in the reservoir which gives us an even further head start for the next winter,” said Britton.

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