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aD Hi ') ~ ABOVE NORMAL PRECIPITATION OVER MOST OF MONTANA HAS CAUSED INCRE.ASES IN TI:I.E PREDICTED SPRING AND SlIHH.ER FLOWS OVER A MONTH AGO. HOWJ::;VER, WATER USERS IN MONTANA, AS WELL AS CENTRAL ARIZONA, WITHOUT STORED WATER MAY EXPERIENCE WATER SliOkTAGr:S. iN MUS'l' uli'itJ<. A.1tE.AS UJ- 'nil:. Wt::~l. t'KU~t't.Cl~ .t-UK :)t'Ki;,G AAU SLitlH..t:k STREAMFLOWS ARE PREDICTED TO BE GOOD TO EXCELLENT. STURAGE IN HAJOk RESERVOIRS THROUGHOUT THE WEST IS ABOVE NORMAL. ~OME FLOODING, ESPECIALLY ALONG UTAH'S WASATCH FRONT, NEVADA'S HUHBOLT RIVER, THE UPPER COLORADO RIVER, AND THE ARKANSAS RIVEk. IS ANTICIPATED THIS SPRING. 1984 Snowmelt Sea.on ea 01 April 1 General Outlook water users without reservoir storage can expect shortages this spring and summer. Precipitation a-.ounts continue to be above normal for southeastern Oregon, northe1l8tern Nevada, central Utah, the Colorado Rockies. and northeastern New Mexico.. Seasonal runoff 1s expected to be much above normal in these areas, with some flooding anticipated this spring. Much of Hontana also received above narmal precipitatian far the lIIOnth of H;:>rch, which brightened the runoff picture somewhat over past predictions. Continued dry weather patterns over California and Arizona have caused further decreases in the predicted water supplies for these states. Snowpack meaaurements indicate record wster content values at msny snow course sites in the Humbolt River Basin, Arkansas River Basin, and the Upper Colorado. River Basin. Snowpack water content levels in the Columbia Bssin generally range above norll181 in the south to below normal in the narth. The water content of the Montana snawpacks increased for the last month due to. above normal rainfall, but are stl11 below to much below normaL Three dry months have left most Cslifornia snowpacks in the Sierras near normal, with some areas much below narmaL Very dry and mild weather has lef~ almost no snow at all an the Arizona watershed. Arizana Above average spring and summer runaff is still farecaat for tI06t cf the Colcrado. Rio Grande, Arv..ans8s. Platte. and Great Basins. Columbia Basin runoff 1s e:lpected to be slightly below normal overall, with belaw normal runoff projected for most of the Mhsauri Basin, and lDllch belaw narmal predicted flows from central Arizona streams. The inflow into Lake Powell is expected to. yield 154 percent of average, with the Rio Grande near 135 percent, the Arkansas near 162 percent of average, and the North and South Platte Rivers at 109 percent and 120 percent, respectively. Almost all streams in the Great Bssin are expected to yield above narmal runoff volumes. with extremes of near 300 percent in the Humbolt Bssin in Nevada and over 70U percent in parr of the Sevier Basin in Utah. The Columbia River is expected to yield 89 percent at The Valles, with the Snake River co.ntributing 98 percent of the 196i-80 average. The Missouri River is expected to yield 81 percent of average at Fort Peck. A paltry 24 percent of normal flows 18 expected down the Salt River into Roosevelt Lake in A:rizona . Reservoir storage throughout the West is excellent, with all states reporting above normal levels for April 1. Basin by Basin Summary SAN JOAQUIN, SACRAMENTO AND NORTH COASTAL BASINS An abnormal precipitation season is expected to produce near normal spring runoff volumes. The dry and mild weather pattern of January snd Pebruary continued through March. 'Ihese three very dry months were preceded by near record precipi tation during October. November. and December. The combination of this abnormal pattern is expected to produce spring runoff volumes in the range of normal conditions. Precipitatian for the month of March averaged 7U percent of normal thraughout California. The driest areas of the stste, with monthly precipitation less than 20 percent of normal, were the extreme southern Sierra, south coast, and southwest deserts. The only area with above narmal precipitation was the Klamath River drainage in the northwest corner of the state. Due to hesvy precipitation during the faU and early winter. and the large volume of water which has alresdy flowed through the main rivers of the Sierra Nevada, the water yesr streamflaw volumes are expected to be above normal. The exception is the Kern River drainage where near normal atreamflow volumes are expected. COLUMBIA BASIN The wster supply outlook. for the Columbia River and Pscific coastal basins csl18 far near normal runoff volumes. 'The westher conditions of March resulted in a slight increase in the projected volumes from last month. Expected runoff from the Canadian portion remains alightly below normal. Farecssts continue to indicste well beloli' normal runoff volumes from the Clsrk. Fork, Flathead. Pend Oreille, and Kootenay Basins. B8sins in esstern . Oregon and louthcentral Idaho are forecast to generate volumes significantly above normal. The Snake River Basin S8 a whole is expected to yield normal volumes this season. Precipitation during the month of March was essentially normal over the bulk of the Columbia River Bssin. Areas significantly above normal included central Oregon. central Idsho, western British Columbia. and northeastern Washington. Areas significantly below no.rmal included western Montana and the Upper Columbia Basins in British Columbia. March precipitation was 89 percent of average for the Columbia Basin above Grand Coulee, 114 percent of average for the Snake River Basin above Ice Harbor, and 113 percent of average for the Columbia Bssin abave The Dalles. Snowpack averages continued abave normal for the southern portion of the Snske drainage and slightly below normal for the remainder af the Columbia Basin. Snowpacks on the Columbia River tributsry basins in Canada continued to. just below normal, while the Kootenay drainage snowpacks were reported at below to far below normal far early April. In Montana, Inow on the Kootenay Basin was less thsn 60 percent of normsl. Other basins in Montana and northern Idaho reported 60 to. 80 percent of their normal snowpacks. Central Oregon, Idaho. and Wyoming snawpacks were about normal. Southern Idaho tributaries to. the Snake River remained well above normal. The Owyhee drainage snowpsck still exceeds 230 percent. Little to no snowpsck was reported in the Oregon and Washington Cascades at low elevations. Higher elevations in the Washington Cascades reported slightly below normal snow. Much below normal snowpack was reported on the west slopes of the Oregon and Washington Cascades. The Olympic Peninsula snd Puget Sound snowpack.s remained far below normal for the early April measurements. The January-July fQrecast for the Columbia River at The Dalles, Oregon, calls for 102 million acte-feet or 93 percent of the 1961-1980 average. At Grande Caulee. Washington. the January-July Calumbia River flow is forecast to be 56.5 million acre-feet or 87 percent of norlllBl. The total contribution from the Snake River Baain. as lEasured at Lower Granite praject, is forecast