Upper North Platte River Basin (8)
February 1999

Snow
The snow courses above Seminoe Reservoir average about 98 percent of average snow water equivalent (SWE) recorded for this time of the year (114 percent of last year). SWE in the drainage area above Northgate is about 97 percent of average and 113 percent of last year at this time. SWE in the Encampment River drainage is about 91 percent of normal and 99 percent of last year. Brush Creek SWE for the year is about 110 percent of normal and 126 percent of last year's SWE. Medicine Bow and Rock Creek drainage SWE is about 94 percent of average and 117 percent of last year at this time. For more information see Basin Summary of Snow Courses at the beginning of this report.

Precipitation
Eleven reporting stations indicate January precipitation was 170 percent of average and about 116 percent of last year's amount. January precipitation varied from 108 to 488 percent of average. Total water-year-to-date precipitation is about 128 percent of average for the basin, which is about 140 percent of last year's amount. Year to date percentages range from 108 to 177.

Reservoirs
Seminoe Reservoir is currently storing about 157 percent of normal for this time of the year. Currently the reservoir is storing 86 percent of last year. Seminoe Reservoir storage is estimated to be 735,200 acre-feet. Last year, at this time, the reservoir had 855,100 acre-feet in storage.

Streamflow
The entire drainage basin is expected to have runoff values from 63 to 106 percent of average. All the following yields are based on the fifty percent chance April through September yield. Yield for the North Platte River near Northgate is expected to be about 286,000 acre-feet (106 percent of average). Encampment River near Encampment is estimated to yield 153,000 acre-feet (98 percent of normal). North Platte River near Sinclair will yield about 734,000 acre-feet (102 percent of normal). Rock Creek near Arlington is estimated to yield 52,000 acre-feet (93 percent of average). Medicine Bow River above Seminoe Reservoir is expected to yield about 80,000 acre-feet (63 percent of normal). Seminoe Reservoir inflow should be about (819,000 acre-feet (96 percent of normal). See the following table for more detailed information on projected runoff. 

  
==================================================================================================================================
                                                  UPPER NORTH PLATTE RIVER BASIN
                                               Streamflow Forecasts - February 1, 1999
==================================================================================================================================
                                              |  <<====== 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      APR-SEP       174       241    |      286       106    |       331       398            271
                                                                    |                       |
Encampment River nr Encampment       APR-SEP       111       136    |      153        98    |       170       195            156
                                                                    |                       |
North Platte River nr Sinclair       APR-SEP       460       623    |      734       102    |       845      1008            719
                                                                    |                       |
Rock Creek nr Arlington              APR-SEP        36        45    |       52        93    |        59        71             56
                                                                    |                       |
Medicine Bow River ab Seminoe Reserv APR-SEP        28        56    |       80        63    |       108       158            127
                                                                    |                       |
Seminoe Reservoir Inflow             APR-JUL       439       630    |      759        96    |       888      1079            788
                                     APR-SEP       473       679    |      819        96    |       959      1165            851
                                                                    |                       |
==================================================================================================================================
                     UPPER NORTH PLATTE RIVER BASIN                     |             UPPER NORTH PLATTE RIVER BASIN
             Reservoir Storage (1000 AF) - End of January               |        Watershed Snowpack Analysis - February 1, 1999
==================================================================================================================================
                                      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    735.2    855.1    467.0 |   N PLATTE above Northgate    8       114        97
                                                                        |
                                                                        |   ENCAMPMENT RIVER            4        99        91
                                                                        |
                                                                        |   BRUSH CREEK                 5       126       110
                                                                        |
                                                                        |   MEDICINE BOW & ROCK CREEK   3       117        94
                                                                        |
                                                                        |   N PLATTE above Seminoe     20       114        98
                                                                        |
==================================================================================================================================
 * 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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