The latest water supply forecast estimates junior water rights holders in the Yakima Basin will receive 75 percent of their allotment this year.

Yakima basin reservoir storage is at 86 percent of average, according to the Bureau of Reclamation’s forecast Monday. The water supply is expected to fully satisfy senior water rights.

The May forecast is based on flows, precipitation, snowpack and reservoir storage as of May 1, along with estimates of future precipitation and river flows.

Chuck Garner, the Yakima Project river operations supervisor, said that robust precipitation — with 15 inches falling by April 19 — led to wetter-than-normal conditions. The month’s total, at 15.9 inches, was 115 percent of average, Garner noted.

“We have seen alternately wet months and dry months this year,” Garner said. “We are hoping May will be moderately wet and not too warm.”

Mountain snowpack declined in April and is between 65 and 70 percent of average. Weak El Nino conditions are likely to continue through the Northern Hemisphere throughout spring and summer.

Gov. Jay Inslee declared a drought emergency in the Upper Yakima Basin last month.

Stream flow and reservoirs

Chris Lynch, a civil engineer with the Bureau of Reclamation, said that adopted stream flow forecasts came from a composite of five forecasts to minimize margin of error and improve accuracy.

Yakima subbasin adopted runoff forecasts from May to July ranged from 53 percent, at Kachess Reservoir, to 89 percent at Rimrock Reservoir, according to Reclamation’s monthly data. Estimated lows differed from estimated highs, in the case of Keechelus, by 43 percent.

“There was a big range,” Lynch acknowledged. “That’s a lot of uncertainty in what might happen in the future.”

Two of the forecasts were high, leaving a little hope that snow will continue to melt and continue to produce runoff, Lynch said.

“We started out the month of April with great snowpack, but ended up with less snow at the end of the month, which is not terribly unusual but left us with less water at the start of May,” Lynch said.

Two reservoirs — Bumping and Rimrock — had higher chances of refilling, at 95 percent and 53 percent respectively. Others had extremely low chances of refilling: 3 percent chances for refill at Keechelus and Kachess and a 5 percent chance for refill at Cle Elum Reservoir among them.

Lynch noted the system was not likely to refill in 2019.

“These numbers aren’t great. Kachess is pretty bad,” he said. “Now that it’s starting to be later in the year, with less snowpack, there really is less time to capture water. We’re losing ground.”

Lynch encouraged irrigation districts to operate for as long as possible with the water available without additional releases, which he said would help “hold things together for as long as possible.”

No irrigation district representatives requested that water be moved at the meeting.

Fish updates

Pat Monk, a fish biologist with the Bureau of Reclamation-Yakima Field Office, noted a number of ongoing projects to monitor fish populations, which included predator surveys in collaboration with the Yakama Nation near Benton City and efforts to tag and track salmon in the lower river.

Monk noted that adult steelhead trout are spawning throughout the basin, with a run size at Prosser of 1,019 wild trout from July 1, 2018, to April 2.

Jonathan Kohr, a state wildlife biologist, noted that five adult steelhead were tagged in Wenas, projecting the total numbers of steelhead in the creek to be between 60 and 80, in addition to 107 logged in Roza.

Following the meeting, Yakima Field Office Manager Chad Stuart said the importance of tracking fish is that short water years affect water levels and the fish in those waters. The last short water year, in 2015, led to a lowered survival rate and not as many fish.

Urban Eberhart, manager for the Kittitas Reclamation District, noted the presentation emphasized the importance of each part of the Yakima Basin Integrated Water Management Plan. The plan is a 30-year, multibillion-dollar project to add water storage, improve fish passage and restore river flows in Kittitas, Yakima and Benton counties.

“We need to have more water conservation measures, more water storage, and continue to work with fish improvements and habitats,” Eberhart said. “The Yakima Basin integrated plan addresses these issues, but it takes time. We’re preparing for the future with the financial constraints we have.”

Weather, water forecasts

This month’s immediate forecast is sunny skies, temperatures in the mid-80s, and overall dry conditions, with the chance of cooling weather and a chance of rain later in the month, according to this month’s presentation.

Spring and summer seasonal outlooks involve higher than normal temperatures and below normal levels of precipitation. Fall also will bring higher than normal temperatures but an equal chance of precipitation, according to the monthly update.

Reclamation will provide water supply forecasts monthly through July, with specific water delivery levels to be determined later in the year after reservoir storage is released to meet demands.

Editorial Note: This article has been updated to clarify that Patrick Monk currently works as a fish biologist for the Bureau of Reclamation.

Reach Lex Talamo at ltalamo@yakimaherald.com or on Twitter: @LexTalamo.