YBSA Monthly Report April, 2015

YBSA Monthly Report

April, 2015

Yakima River Basin Drought 2015: Today we have a full reservoir system at about 99% and normally that would occur in early June.

The outflows from the reservoirs exceed inflow because of irrigator demand and required flows for fish. The fish flows have been quantified for a minimum in terms of flow at a geographical point in the system called Parker, just below Union Gap, based on monthly TWSA (Total Water Supply Available) estimates from the U.S. Bureau of Reclamation. The minimum flow is 300 cfs. That equates to 5 months at 600 acre/feet per day, or 90,000 acre/feet.

However, in the spring there can be periods when pulse flows are needed to transport the juveniles out to the Columbia, on the order of 10,000-20,000 acre/feet. We don’t know what fish needs would be if flows were so low that river water temperatures are higher than 69 degrees, as that is the temperature at which critical problems begin to occur, and at 78 degrees mortality approaches 100%. That either kills the fish or keeps them out of the river, in which case more water will be needed to allow them to move to their spawning areas. Those temperature can occur in dry years when a lesser amount of water is available in the river. Dead fish in the river from high temperatures would be a very dramatic event.

Senior water rights total 1,091,000 acre/feet, juniors 1,315,000 acre/feet, combined total of 2,406,000 acre/feet. Our storage totals are only 1,065,000 acre/feet, or just a little less than the senior water rights. The rest must come from snow-pack.

Today we are at 15% of our normal snow-pack (6% in upper basin, 23% in the lower, average = 15%). (ftp://ftp.wcc.nrcs.usda.gov/data/water/wcs/gis/maps/wa_swepctnormal_update.pdf The June estimate will determine the amount of water available for fish and agriculture.

At this point in time the U.S. Bureau of Reclamation estimates junior water rights to receive 54% of their allotment. The forecast is for below normal precipitation, and above normal temperatures. In the past 25 years the Yakima Basin has been able to survive using ground water, conservation, and water transfers from idled acres in exchange for money. Most irrigators are hoping the U.S. Bureau of Reclamation estimate is right.

This could be the driest year since post war times, we won’t know until the irrigation season is over. The most significant drought relief measure is to pump ground water. It is a possibility that the well yields will be significantly less than historical production, due to increased demand for ground water and the accumulation of 10 more years of well drilling and pumping. It is noted that with the forecasted estimates for next year are continued below normal precipitation and above normal temperatures 2016 will be devastating to both fish and agriculture.

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