IntermtntClimateSummaryJune2006 - Laserfiche WebLink

Home Browse Search

INTERMOUNTAIN WEST CLIMATE SUMMARY, JUNE 2006 Wyoming Water Availability June 2006 Source: Wyoming Water Resources Data System and USDA Natural Resources Conservation Service USGS reports that most steamflo\;v gauges (Figure 8a) for western and south central Wyoming are mostly in the normal category (25th to 75th percentile), with some areas of high flow in the Shoshone and Upper Green Rivers. Low flows are recorded in the northern part of Wyoming on the Snake, Po\;vder and Wind Rivers and in the southeast on the Upper and Lower Platte Rivers. The Surface Water Supply Index (SWSI) values (Figure 8b) are similar to streamflo\;v: in the near normal category in \;vestern and south-central Wyoming and lo\;ver in other areas. The SWSI indices decreased for nearly all basins during May. The driest basins are the Wind, Po\;vder and Big Horn River basins~ they are in moderate to severe drought categories. The Lower North Platte, Laramie and Upper North Platte in the southeast section of Wyoming are also belo\;v zero, in a mild to moderate drought category. There was a slight increase in SWSI values from April, 2006 for the Shoshone and Powder River Basins. According to the NWS, Riverton, the Lander/Riverton area received only 3% of normal precipitation in May 2006, making it the driest May on record since 1892. Notes The "7 -day average streamflow" map (Figure 8a) shows the average streamflow conditions for the past 7 days compared to the same period in past years. By averaging over the past 7 days, the values on the map are more indicative of longer-term streamflow conditions than either the "Real-time streamflow" or the "Daily streamflow" maps. If a station is categorized in "near normal" or 25th - 75th percentile class, it means that the streamflows are in the same range as 25-750/0 of past years. Note that this "normal" category rep- resents a wide range of flows. Only stations hav- ing at least 30 years of record are used. Areas containing no dots indicate locations where flow data for the current day are temporarily unavail- able. The data used to produce this map are pro- visional and have not been reviewed or edited. They may be subject to significant change. The Surface Water Supply Index (SWSI-Figure 8b) is computed using only surface water supplies for the drainage. The computation includes reservoir storage, if applicable, plus the forecast runoff. The index is purposely created to resemble the Palmer Drought Index, with normal conditions centered near zero. Adequate and excessive supply has a positive number and deficit water supply has a negative value. Soil moisture and forecast precipitation are not considered as such, but the forecast runoff may consider these values. Legend > 4.0 3.0 2.0 1.0 0.5 0.0 -0.5 -1.0 -2.0 -3.0 <-4.0 V.-.J" r-..... . . o . . . . 0 High >900/0 75-890/0 25-750/0 10-240/0 <100/0 Low Not Ranked Figure 8a. Wyoming Percentile Streamflow Conditions (updated 6/11/06). Extremely Wet Very Wet Moderately Wet Slightly Wet Incipient Wet Spell Near Normal Incipient Dry Spell Mild Drought Moderate Drought Severe Drought Extreme Drought \ I Powder I -2.M I J- T ! \ Lower Nokh . ~(atte I t ~..., Upper Sna ke OA9 -2_39 I I 1- Figure 8b. Wyoming Surface Water Supply Index (data through 6/1/06) On the Web - Information on current Wyoming snowpack, SWE, and SWSI, along with more data about current water supply status for the state, can be found at: http://www.wrds.uwyo.edu/wrds/nrcs/nrcs.html. - The Palmer Drought Index is found on NOAA's drought page: www.drought.noaa.gov. - For current streamflow information from USGS, visit: http://water.usgs.gov/waterwatch/ - For current maps of SWE as a percent of normal like in Figure 8a, go to: http://www.wcc.nrcs.usda.gov/gis/snow.html. RECENT CONDITIONS 111