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May 13, 2016 5 CapitalPress.com Water April heat produces dramatic PNW snowmelt Capital Press An April heatwave pro- duced dramatic melting of the mountain snowpacks in Ida- ho, Oregon and Washington, quickly fi lling reservoirs but leading to worries in some ar- eas that late-season water could be scarce. Idaho Parts of Idaho lost a record amount of mountain snowpack during April, according to hy- drologists at the USDA Natural Resources Conservation Ser- vice. As a result, peak stream- fl ows are occurring two to three weeks ahead of normal, and the streamfl ow forecast has shrunk to 70 to 90 percent of average throughout most of the state, NRCS hydrologist Phil Mor- risey said. Morrisey said the snowpack now ranges from 55 to 85 per- cent of normal throughout the state, with the greatest snow- pack losses occurring from Treasure Valley north through the Panhandle. He said the declines were the result of dry weather and high temperatures, which av- eraged 3 to 10 degrees above normal. “This year we saw more (April) decline in the snowpack than in any of the other years we’ve looked at it,” Morrisey said. Streamfl ow volumes for April were more than 175 per- cent of normal in the Bound- ary, Bruneau, Deadwood, Big Wood, Big Lost, Snake near Moran and Willow Creek drainages, as well as parts of the Salmon and Boise drainag- es. The headwaters of the Snake River at the Wyoming border received just one-third of usual April precipitation, and most of the state’s basins received 40 to 60 percent of their usual mois- ture for the month. Southern Idaho was the ex- ception to the dry month, with April precipitation at 112 per- cent of normal in the Owyhee Basin, more than 150 percent of normal in the Bruneau, Jar- bidge and Salmon Falls basins and 130-140 percent of normal in the Oakley and Raft River basins. Morrisey said based on cur- rent natural-fl ow and storage conditions, marginally ade- quate supplies are anticipated in the Big Lost, Little Lost and Big Wood basins. Morrisey said reservoirs have above-normal fi ll throughout the state and are capturing the runoff, which has been aided in reaching streams by ample soil moisture. Lynn Harmon, general manager of the Big Wood Ca- nal Co., said his irrigators rely mostly on storage water, and the early melting has helped his water outlook, given that peak fl ows were fi lling reservoir storage before irrigators with senior natural-fl ow rights up- stream started diverting. April changed that. “This year highlights not only the importance of peak snowpack quantity, but also the importance of the rate, timing and amount of snowmelt,” the NRCS said in its Oregon report. Normally, melting snow feeds streams at a slower pace that sustains the water supply later into summer, the NRCS said. Spring rains will be come more important factors than usual, the agency said. “If plentiful, it could help delay irrigation demand and increase reservoir storage, po- tentially offsetting or buffering the impacts of early snowmelt,” the agency’s snow survey team concluded. Washington April was a month of rapid snowmelt in the Washington Cascades giving irrigators plenty of water, but it may not last into late summer in valleys with little or no reservoirs. Pear orchards in some parts of the Wentachee Valley, or- chards to the north in the En- tiat Valley and orchards and hay fi elds even farther north in the Methow and Okanogan valleys may run low on water in August and September. Junior water right holders in the Yakima Basin are fore- cast at 85 percent of the nor- mal supply by late summer, the U.S. Bureau of Reclamation announced May 5. That shouldn’t affect irriga- tors such as the Roza Irrigation District and Kittitas Reclama- tion District but means they and other juniors will need to be careful with water, a USBR offi cial said. “We’ve seen the fastest melt rate we’ve ever seen — record rates or second-fastest rates in over 80 percent of our SNOTEL (snowpack teleme- try) sites with 15 years or more of data,” said Scott Pattee, wa- ter supply specialist with the NRCS in Mount Vernon. “Sites below 5,000 feet have melted out two to three weeks early and right now the snow level is 5,000 to 5,500 feet,” Pattee said. Statewide snowpack was 107 percent of normal on April 5 but had dropped to 73 percent of normal by May 4, he said. The best snowpack all winter was in the upper Columbia, but that’s now 68 percent versus 134 percent a month ago, he said. May 5 through September streamfl ow forecasts are re- fl ecting the earlier than desired loss of snowpack, Pattee said. Rapid snowmelt has caused the highest unregulated fl ows in the Yakima River at the USBR station at Parker in the past 35 years and the second-highest in the past 90 years, said Chris Lynch, a USBR hydrologist in Yakima. The Wenatchee River and other rivers draining the east slopes of the Cascades have been running full for a month. The only thing that’s prevent- ed fl ooding has been that there was little to no rain, Pattee said. Precipitation at the fi ve wa- ter reservoirs in the Yakima Basin was 14 percent of aver- age in April, which is a new record, beating 15 percent for that month set in the 1930s and 1950s, Lynch said. “I don’t want to raise any big alarms, but it’s a very inter- esting statistic,” he said. It means April was a dry month, which by itself may not mean much but would if March had been dry, he said. May usu- ally is drier than April. As of May 3, the fi ve Yakima reser- voirs were 94 percent full and at 126.7 percent of the average from 1981 through 2010. “We hope to have them full Western U.S. snow water equivalent Basin-wide percent of 2016 snowpack compared to the aggregate average (1971-2010). 72 80 37 40 71 75 49 67 68 57 41 52 74 59 41 6 2 46 46 67 41 38 56 47 27 61 43 77 56 47 62 62 57 62 10 65 50 54 63 71 53 45 64 62 68 61 34 55 78 55 76 35 66 68 36 23 65 35 123107 141 35 107 66 141 75 77 70 126 168 141 72 88 95 118 138 121 68 101 106 72 202 150 121 73 109 64 93 138 116 120 110 160 118 110 48 119131 5 105 177 156 1850 104 120 Percentage key (As of May 9) 74 0 Unavailable Less than 50% 50-69% 70-89% 90-109% 110-129% 130-149% More than 149% Miles 0 Source: USDA, Natural Resources Conservation Service by mid to late May and be able to make it into June before we 150 300 Capital Press graphic start drawdowns for irrigation,” Lynch said. This is a don’t miss sale! Oregon April’s heatwave was so in- tense that nine automated snow monitoring sites in Oregon re- corded the most dramatic April snowmelt on record. Among monitoring sites that typically have snow on May 1, 75 percent lost between 3 and 4 feet of snow in the month, according to the USDA’s Nat- ural Resources Conservation Service. The early runoff helped fi ll reservoirs around the state, but means streamfl ows will be below normal this spring and summer, especially in Southern and southeastern Oregon, the NRCS reported in its May wa- ter supply bulletin. “Once the snow is gone, streams will be at the whim of temperatures and spring rainfall,” the NRCS Portland snow survey team reported. The National Oceanic and At- mospheric Administration’s Climate Prediction Center said the state can expect above nor- mal temperatures for the next three months, although with above normal rain in Southern Oregon. 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