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COLORADO <br /> WATER SUPPLY CONDITIONS UPDATE <br /> FROM THE OFFICE OF THE STATE ENGINEER; COLORADO DIVISION OF WATER RESOURCES January, 1999 <br /> ROOM 818,1313 SHERMAN ST.,DENVER,CO 80203; (303)-866-3581 <br /> W W W.DNR.STATE.CO.US/ <br /> A general decline in snowpack over the month of December, measured as percent of average water content by the <br /> U.S.D.A. Natural Resources Conservation Service, is believed to be the cause of the reduction in this month's SWSI values <br /> from December 1. Statewide the snowpack averages 77%of normal. The lowest snowpack conditions,65%of average,were <br /> in the Colorado and Yampa/White River basins while the Rio Grande was the only basin with a value above average, at <br /> 105%. Wide variations in snowpack conditions are illustrated within the Arkansas basin which contains a 22%of average <br /> reading in the Apishapa River drainage and a 110% of average reading in the Wet Mountain Valley drainage. <br /> In spite of the 105% of average snowpack value, Rio Grande basin administrator's visual observations indicate a <br /> deficiency of snowpack and a concern about conditions. Reports from most basin administrators referred to low December <br /> precipitation and low snowpack. Stream flows have been maintaining near normal base flow rates. <br /> The Surface Water Supply Index (SWSI) developed by this office and the U.S.D.A. Natural Resources Conservation <br /> Service is used as an indicator of mountain based water supply conditions in the major river basins of the state. It is based <br /> on snowpack,reservoir storage,and precipitation for the winter period (November through April). During the winter period <br /> snowpack is the primary component in all basins except the South Platte basin where reservoir storage is given the most <br /> weight. The following SWSI values were computed for each of the seven major basins for January 1, 1999 and reflect <br /> conditions during the month of December. <br /> January 1, 1999 Change From Change From <br /> Basin SWSI Value Previous Month Previous Year <br /> South Platte 1.0 -1.2 -2.0 <br /> Arkansas -1.1 -1.5 -1.9 <br /> Rio Grande 1.5 -1.5 +2.4 <br /> Gunnison -0.9 -2.0 -0.5 <br /> Colorado -0.6 -0.8 -0.7 <br /> Yampa/WhiteYrfl.e (` a• -1.6 -0.5 <br /> San Juan/Dolores -0.9 -3.7 -0.6 <br /> SCALE <br /> -4 -3 -2 -1 0 +1 +2 +3 +4 <br /> Severe Moderate Near Normal Above Normal Abundant <br /> Drought Drought Supply Supply Supply <br /> 1 <br />