Upper North Platte River Basin (8)
March 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 (108 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 94 percent of normal and 106 percent of last year. Brush Creek SWE for the year is about 111 percent of normal and 115 percent of last year's SWE. Medicine Bow and Rock Creek drainage SWE is about 94 percent of average and 119 percent of last year at this time. In the North Platte River above Seminoe Reservoir, SWE is about normal (112 percent of last year. For more information see Basin Summary of Snow Courses at the beginning of this report.

Precipitation
Eight reporting stations indicate February precipitation was 117 percent of average and about 117 percent of last year's amount. February precipitation varied from 67 to 230 percent of average. Total water-year-to-date precipitation is about 125 percent of average for the basin, which is about 131 percent of last year's amount. Year to date percentages range from 108 to 151.

Reservoirs
Seminoe Reservoir is currently storing about 172 percent of normal for this time of the year. Currently the reservoir is storing 84 percent of last year and 69 percent of capacity. Seminoe Reservoir storage is estimated to be 705,200 acre-feet. Last year, at this time, the reservoir had 837,500 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 50,000 acre-feet (89 percent of average). Medicine Bow River above Seminoe Reservoir is expected to yield about 73,000 acre-feet (58 percent of normal). Seminoe Reservoir inflow should be about (815,000 acre-feet (96 percent of normal). See the following table for more detailed information on projected runoff. 

==================================================================================================================================
                                                  UPPER NORTH PLATTE RIVER BASIN
                                               Streamflow Forecasts - March 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       166       237    |      286       106    |       335       406            271
                                                                    |                       |
Encampment River nr Encampment       APR-SEP       109       135    |      153        98    |       171       197            156
                                                                    |                       |
North Platte River nr Sinclair       APR-SEP       443       617    |      735       102    |       853      1027            719
                                                                    |                       |
Rock Creek nr Arlington              APR-SEP        33        43    |       50        89    |        58        70             56
                                                                    |                       |
Medicine Bow River ab Seminoe Reserv APR-SEP        22        49    |       73        58    |       102       154            127
                                                                    |                       |
Seminoe Reservoir Inflow             APR-JUL       455       634    |      755        96    |       876      1055            788
                                     APR-SEP       491       684    |      815        96    |       946      1139            851
                                                                    |                       |
==================================================================================================================================
                     UPPER NORTH PLATTE RIVER BASIN                     |             UPPER NORTH PLATTE RIVER BASIN
             Reservoir Storage (1000 AF) - End of February              |        Watershed Snowpack Analysis - March 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    705.2    837.5    409.0 |   N PLATTE above Northgate    8       108        98
                                                                        |
                                                                        |   ENCAMPMENT RIVER            4       106        94
                                                                        |
                                                                        |   BRUSH CREEK                 5       115       111
                                                                        |
                                                                        |   MEDICINE BOW & ROCK CREEK   3       119        94
                                                                        |
                                                                        |   N PLATTE above Seminoe     20       112       100
                                                                        |
==================================================================================================================================
 * 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.
(D) - The operational measurement of flow at this point has been discountinued.
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