Despite a dry spring and record heat in the early summer, the Yakima River Basin came through with an above-average supply of water.
U.S. Bureau of Reclamation officials credited near-average precipitation through the year, bolstered by an increase in rain in September. Cooler weather later in the season also helped ensure the basin’s five reservoirs were delivering water to all users.
“We had a good year,” Doug Call, BOR’s river operator, said during a Thursday meeting on the state of the basin’s water supply. “Thanks for everyone’s help.”
And forecasters are anticipating a wetter fall and early winter for the region that should bring reservoir levels back up.
The 2020-21 water year, which ended Sept. 30, saw precipitation at 97.1% of the average, despite experiencing the fourth-driest March on record.
But Revell said the basin went into the season with a good snowpack in the Cascades, and cooler weather in the spring that attenuated runoff until summer. He said the basin was lucky to get that snowpack, which came from storms originating in Asia and crossing the Pacific.
“I equate it to a 100-foot putt,” Revell said. “You hit the ball, and anything can bump it.”
But the summer saw a record-setting heat wave, with a drought emergency being declared through most of the state.
While the water supplies were good, water managers were carefully watching the situation with the reservoirs.
“In a sense, we were kind of thinking that the reservoirs were going to keep drafting, and then things moderated, and demand backed down,” said Chris Lynch, BOR operations engineer. “We ended up with above-average storage.”
Call said total carryover storage in the five reservoirs — Kachess Lake, Keechelus Lake, Cle Elum Lake, Bumping Lake and Rimrock Lake — was at 105% of average. As of Friday, Keechelus was at 26% capacity, Kachess was at 50%, Cle Elum 21%, Bumping Lake at 38% and Rimrock at 32%.
Lynch said Cle Elum Lake saw heavier use this year as water was released to allow construction on a project there. Rimrock, which is at about its average capacity for this time of year, has the most water and the largest potential for refilling over the winter, he said.
While fire crews used water from Bumping Lake to battle the Schneider Springs Fire, Lynch said that did not affect water supplies.
“They did use our reservoir for helicopter dips, but it was kind of taking a sip compared to our taking water,” Lynch said.
Lynch said every water user, including junior rights holders such as the Roza District, received full allotments. In times of drought, junior rights holders’ allotments can be cut to ensure that senior rights holders receive their full share of water.
The last time that cut was made was 2019. Revell said the Roza District will extend its irrigation season to Oct. 20, allowing growers to boost moisture in their soil before winter.
“All told, it was a good year. We’re not complaining,” Revell said.
And the coming months appear to bode well for water supplies. In the 90-day forecast, Washington is expected to get above-average precipitation, with 115-151% of average rain expected in Eastern Washington in October, and 129-232% in Western Washington and along the Cascade Ridge, said Mik Lewicki, a hydrologist with the BOR.
Lewicki said a La Niña event is also expected in coming months, which means that more wet weather can be expected in the Pacific Northwest in the winter.