Upper North Platte River Basin (8)
February 2000

Snow
The snow courses above Seminoe Reservoir have about 82 percent of average snow water equivalent (SWE) recorded for this time of the year (83 percent of last year). SWE in the drainage area above Northgate is about 90 percent of average and 92 percent of last year at this time. SWE in the Encampment River drainage is about 74 percent of normal and 81 percent of last year. Brush Creek SWE for the year is about 85 percent of normal and 78 percent of last year's SWE. Medicine Bow and Rock Creek drainage SWE is about 67 percent of average and 71 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 January precipitation was 89 percent of average and about 146 percent of last year's amount. January precipitation varied from 25 percent of average at Wamsutter to 176 percent of average at Willow Creek PS SNOTEL. Total water-year-to-date precipitation is about 78 percent of average for the basin, which is about 62 percent of last year's amount. Year to date percentage ranges from 46 to 96 for the 8 reporting stations.

Reservoirs
Seminoe Reservoir is currently storing about 156 percent of normal for this time of the year. Currently, the reservoir is storing 112 percent of last year's amount. Currently, Seminoe Reservoir storage is estimated to be storing 845,600 acre-feet (83 percent of capacity). Last year, at this time, the reservoir had 756,700 acre-feet in storage.

Streamflow
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 156,000 acre-feet (58 percent of average). Encampment River near Encampment is estimated to yield 63,000 acre-feet (40 percent of normal). North Platte River near Sinclair will yield about 358,000 acre-feet (50 percent of normal). Rock Creek near Arlington is estimated to yield 44,000 acre-feet (79 percent of average). Medicine Bow River above Seminoe Reservoir is expected to yield about 57,000 acre-feet (45 percent of normal). Seminoe Reservoir inflow should be about (423,000 acre-feet (50 percent of normal). See the following table for more detailed information on projected runoff. 

==================================================================================================================================
                                                  UPPER NORTH PLATTE RIVER BASIN
                                               Streamflow Forecasts - February 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      APR-SEP        88       155    |      200        74    |       245       312            271
                                                                    |                       |
Encampment River nr Encampment       APR-SEP        70        95    |      112        72    |       129       154            156
                                                                    |                       |
North Platte River nr Sinclair       APR-SEP       241       404    |      515        72    |       626       789            719
                                                                    |                       |
Rock Creek nr Arlington              APR-SEP        34        43    |       50        89    |        57        69             56
                                                                    |                       |
Medicine Bow River ab Seminoe Reserv APR-SEP        26        52    |       75        59    |       102       151            127
                                                                    |                       |
Seminoe Reservoir inflow             APR-JUL       230       421    |      550        70    |       679       870            788
                                     APR-SEP       254       460    |      600        71    |       740       946            851
                                                                    |                       |
==================================================================================================================================
                     UPPER NORTH PLATTE RIVER BASIN                     |             UPPER NORTH PLATTE RIVER BASIN
             Reservoir Storage (1000 AF) - End of January               |        Watershed Snowpack Analysis - February 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    830.1    735.2    467.0 |   N PLATTE above Northgate    8        92        90
                                                                        |
                                                                        |   ENCAMPMENT RIVER            4        81        74
                                                                        |
                                                                        |   BRUSH CREEK                 5        78        85
                                                                        |
                                                                        |   MEDICINE BOW & ROCK CREEK   3        71        67
                                                                        |
                                                                        |   N PLATTE above Seminoe     20        83        82
                                                                        |
==================================================================================================================================
 * 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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