As the summer season heats and dries the Kittitas Valley, the water supply in the Yakima Basin has grown thinner.

The most recent report from the Bureau of Reclamation predicts junior water rights holders in the basin will receive 67 percent of their normal water allotment for the season, while senior water rights holders will retain 100 percent. The 67 percent number is down from the last forecast in mid-June, which stood at 72 percent. Basin storage is currently at 80 percent of average, with basin reservoirs reporting a collective 68 percent capacity. Gov. Jay Inslee declared a drought emergency for the Upper Basin on April 4, extending the declaration to the Lower Basin on May 20.

Bureau Hydrologist Chris Lynch said the bureau conducts monthly runoff forecasts that predict how much water will flow out of the basin from the beginning of the month until the end of September. Measurements are taken at a gauge near Parker Dam on the Yakima River, because most of the diversions are above that point, the last major one being the Sunnyside Valley Irrigation District diversion.

“We manage a minimum flow there,” he said. “We have a good handle then on what the demands are above that point. If we estimate what the natural runoff will be at that point, we can tell kind of what the supply is.”

Lynch said the bureau also looks at reservoir levels at the start of the month along with potential runoff from what snowpack is left in coming months. The bureau uses forecasts from multiple agencies to come up with an estimate for that, one example being a daily forecast from the River Forecast Center in Portland. That forecast takes snow levels, temperature and precipitation predictions into account, as well as historical data comparisons. The results are called an extended streamflow prediction, and Lynch said that predicts the streamflow volumes for the coming period.

Lynch said that forecast along with others and some in-house predictions are taken into account to create an estimate on how much available water there will be for irrigation. He said some predictions come in on either the low end or the high end, while some come in right in the middle.

“I look at all those and determine an adopted forecast,” he said. “I took into account all of them. Of course, they’re not all going to be right. There’s going to be one right answer.”

Lynch said he follows a middle ground in making his prediction, although he said his prediction came in slightly below the average of all the predictions he used. With most of the snowpack being gone and precipitation being insignificant during this period of summer, he said it is easier to predict how the flows will decline at this point.

“It turns out that it seems based on the way the actual flows are right now that the low end forecast that was put out by the NRCS is more correct than the high-end forecast,” he said. “We’re kind of on the low end of the forecast from the different agencies.”

Lynch said the bureau will do a mid-month forecast for July, as well as another in early August

“There is still some room for variation,” he said. “Every time I do it, more evidence is revealed, so to speak. We don’t just want to sit back and say we think we got it. Every time we want to reevaluate it with fresh eyes. I think it’s going to stay in this range pretty tight now. I think we have a number that’s close to being right.”

LOCAL IRRIGATORS

Urban Eberhart with the Kittitas Reclamation District said the focus for the district is to run water as efficiently as possible, and while prorationing is in effect, the goal is to extend water usage for as long as possible during the growing season.

“We are going to attempt to stretch that water supply to approximately Sept. 15 if we do not get any further cuts from the Bureau of Reclamation,” he said.

Eberhart said it is important that the district makes the water last until that period in September, as they want to ensure that later season crops like corn can get finished.

“We have crops that need water later in the season,” he said. “What we’re doing is lowering the daily diversion amounts at Easton in order to get to that point in time. We’ll be running a little more water in July and August and when we get into September, we’ll be cutting it back significantly so that we can make it for that two-week period of time for the later crops in the district.”

The mid-September cutoff date is approximately four weeks ahead of normal. With 100 percent prorationing last year, the cutoff date was Oct. 15. Eberhart said the last time the district saw prorationing at this level was in 2015. With investments in conservation, including the ongoing canal lining projects undertaken by the district, Eberhart said the district has not been blindsided by the situation.

“From the beginning, as we were watching the water coming out of the hills, watching the supply, we were all along anticipating about a 70 percent supply,” he said. “We were not anticipating a 67 percent supply, but we had been managing all along for about 70 because we didn’t think it was as optimistic as what the early numbers were. That made it more possible for us to be prepared for what actually occurred.”

Eberhart said weather conditions are also different than in 2015, with cooler temperatures helping stave off evaporation. This and a more diverse mix of crops in the valley, including alfalfa, sunflowers, beans and corn helps break up the timing of the water orders.

“It’s not all just one crop,” he said. “A lot of those other crops use less water than the timothy, so that’s helped us stretch. Conservation and a more diverse crop mix have made the ability to distribute this supply different, and it’s actually working out for us.”

With the basin experiencing fluctuations in water supply from year to year, Eberhart said the issue underscores the importance of continued funding and work within the Yakima Basin Integrated Plan. Between 2019-2020, he said the district will be implementing approximately $10 million in studies and design work related to conservation, surface and groundwater storage and utilization.

“We’re going to continue and are continuing to improve this distribution system and make it so it can store more water so we can get better water deliveries to the farms,” he said. “We’re also going to continue our tributary supplementation program, so that we are able to help the fish and wildlife at the same time we’re making better deliveries to the farms.”

Eberhart said these programs will help growers more effectively cope with what he says will be a more common occurrence.

“This really is forecast to be the new average in the future,” he said. “This would just be an average year. You go out about 20 years and you look at multiple forecasts, and this could be what we’re just faced with every year on average.”

With future projections showing less and less water available for irrigators on a yearly basis, Eberhart said the authorization of the first development phase of YBIP will put the gears into motion, eventually creating an infrastructure that will alleviate the yearly stress of basin growers.

“We have state, federal and local support for this plan,” he said. “We just need to keep it moving forward and incrementally bring all the elements together and implement them. We will get there.”

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