Upper North Platte River Basin (8)
June 2000

Snow
The snow courses above Seminoe Reservoir have about 36 percent of average snow water equivalent (SWE) recorded for this time of the year (28 percent of last year). SWE in the drainage area above Northgate is about 43 percent of average and 43 percent of last year at this time. SWE in the Encampment River drainage is about 29 percent of normal and 23 percent of last year. Brush Creek SWE for the year is about 43 percent of normal and 23 percent of last year's SWE. Medicine Bow and Rock Creek drainage SWE is about 30 percent of average and 19 percent of last year at this time. For more information see Basin Summary of Snow Courses at the beginning of this report.

Precipitation
Eight reporting stations indicate May precipitation was 123 percent of average and about 96 percent of last year's amount. May precipitation varied from 89 to 254 percent of average. Total water-year-to-date precipitation is about 91 percent of average for the basin, which is about 77 percent of last year's amount. Year to date percentage ranges from 73 to 111 percent of average for the 8 reporting stations.

Reservoirs
Seminoe Reservoir is currently storing about 166 percent of normal for this time of the year. Currently, the reservoir is storing 108 percent of last year's amount. Currently, Seminoe Reservoir storage is estimated to be storing 914,000 acre-feet (90 percent of capacity). Last year, at this time, the reservoir had 842,900 acre-feet in storage.

Streamflow
All the following yields are based on the fifty percent chance June through September yield. Yield for the North Platte River near Northgate is expected to be about 120,000 acre-feet (76 percent of average). Encampment River near Encampment is estimated to yield 73,000 acre-feet (71 percent of normal). North Platte River near Sinclair will yield about 315,000 acre- feet (73 percent of normal). Rock Creek near Arlington is estimated to yield 17,600 acre-feet (42 percent of average). Medicine Bow River above Seminoe Reservoir is expected to yield about 25,000 acre-feet (39 percent of normal). Seminoe Reservoir inflow should be about (340,000 acre-feet (69 percent of normal). See the following table for more detailed information on projected runoff.

==================================================================================================================================
                                                  UPPER NORTH PLATTE RIVER BASIN
                                               Streamflow Forecasts - June 1, 2000
==================================================================================================================================
                                              |  <<====== Drier ======  Future Conditions  =======  Wetter =====>>  |             
                                              |                                                                     |
  Forecast Point                     Forecast |  ==================== Chance Of Exceeding * ======================  |
                                      Period  |    90%       70%    |  50% (Most Probable)  |      30%       10%    |  30-Yr Avg.
                                              | (1000AF)  (1000AF)  |   (1000AF)  (% AVG.)  |    (1000AF)  (1000AF) |    (1000AF)
====================================================================|=======================|=====================================
North Platte River nr Northgate      JUN-SEP        87       107    |      120        76    |       133       152            158
                                                                    |                       |
Encampment River nr Encampment       JUN-SEP        42        60    |       73        71    |        86       104            103
                                                                    |                       |
North Platte River nr Sinclair       JUN-SEP       208       272    |      315        73    |       358       422            431
                                                                    |                       |
Rock Creek nr Arlington              JUN-SEP      15.0      16.5    |     17.6        42    |      18.7        21             42
                                                                    |                       |
Medicine Bow River ab Seminoe Reserv JUN-SEP      13.5      19.9    |       25        39    |        31        40             64
                                                                    |                       |
Seminoe Reservoir inflow             JUN-JUL       184       247    |      290        68    |       333       394            428
                                     JUN-SEP       166       270    |      340        69    |       410       514            491
                                                                    |                       |
==================================================================================================================================
                     UPPER NORTH PLATTE RIVER BASIN                     |             UPPER NORTH PLATTE RIVER BASIN
             Reservoir Storage (1000 AF) - End of May                   |        Watershed Snowpack Analysis - June 1, 2000
==================================================================================================================================
                                      Usable |  *** Usable Storage ***  |                            Number     This Year as % of
Reservoir                            Capacity|  This      Last          |   Watershed                  of       =================
                                             |  Year      Year     Avg  |                          Data Sites   Last Yr   Average
========================================================================|=========================================================
SEMINOE                               1016.7    914.2    842.9    551.0 |   N PLATTE above Northgate    5        43        43
                                                                        |
                                                                        |   ENCAMPMENT RIVER            3        23        29
                                                                        |
                                                                        |   BRUSH CREEK                 2        23        43
                                                                        |
                                                                        |   MEDICINE BOW & ROCK CREEK   2        19        30
                                                                        |
                                                                        |   N PLATTE above Seminoe     13        28        36
                                                                        |
==================================================================================================================================
 * 90%, 70%, 30%, and 10% chances of exceeding are the probabilities that the actual volume will exceed the volumes in the table.

The average is computed for the 1961-1990 base period.

(1) - The values listed under the 10% and 90% Chance of Exceeding are actually 5% and 95% exceedance levels.                  
(2) - The value is natural volume - actual volume may be affected by upstream water management.


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