Upper North Platte River Basin (8)
May 2000

Snow
The snow courses above Seminoe Reservoir have about 80 percent of average snow water equivalent (SWE) recorded for this time of the year (78 percent of last year). SWE in the drainage area above Northgate is about 96 percent of average and 99 percent of last year at this time. SWE in the Encampment River drainage is about 73 percent of normal and 73 percent of last year. Brush Creek SWE for the year is about 72 percent of normal and 64 percent of last year's SWE. Medicine Bow and Rock Creek drainage SWE is about 64 percent of average and 60 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 April precipitation was 83 percent of average and about 54 percent of last year's amount. April precipitation varied from 47 to180 percent of average. Total water-year-to-date precipitation is about 87 percent of average for the basin, which is about 74 percent of last year's amount. Year to date percentage ranges from 71 to 114 percent of average for the 8 reporting stations.

Reservoirs
Seminoe Reservoir is currently storing about 192 percent of normal for this time of the year. Currently, the reservoir is storing 105 percent of last year's amount. Currently, Seminoe Reservoir storage is estimated to be storing 753,000 acre-feet (74 percent of capacity). Last year, at this time, the reservoir had 719,800 acre-feet in storage.

Streamflow
All the following yields are based on the fifty percent chance May through September yield. Yield for the North Platte River near Northgate is expected to be about 203,000 acre-feet (89 percent of average). Encampment River near Encampment is estimated to yield 104,000 acre-feet (70 percent of normal). North Platte River near Sinclair will yield about 511,000 acre-feet (81 percent of normal). Rock Creek near Arlington is estimated to yield 31,000 acre-feet (56 percent of average). Medicine Bow River above Seminoe Reservoir is expected to yield about 63,000 acre-feet (60 percent of normal). Seminoe Reservoir inflow should be about (574,000 acre-feet (78 percent of normal). See the following table for more detailed information on projected runoff. 

==================================================================================================================================
                                                  UPPER NORTH PLATTE RIVER BASIN
                                               Streamflow Forecasts - May 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      MAY-SEP       142       178    |      203        89    |       228       264            228
                                                                    |                       |
Encampment River nr Encampment       MAY-SEP        69        90    |      104        70    |       118       139            148
                                                                    |                       |
North Platte River nr Sinclair       MAY-SEP       337       441    |      511        81    |       581       681            631
                                                                    |                       |
Rock Creek nr Arlington              MAY-SEP        24        28    |       31        56    |        34        39             55
                                                                    |                       |
Medicine Bow River ab Seminoe Reserv MAY-SEP        29        48    |       63        60    |        80       109            105
                                                                    |                       |
Seminoe Reservoir inflow             MAY-JUL       340       450    |      525        78    |       600       705            671
                                     MAY-SEP       372       492    |      574        78    |       656       770            733
                                                                    |                       |
==================================================================================================================================
                     UPPER NORTH PLATTE RIVER BASIN                     |             UPPER NORTH PLATTE RIVER BASIN
             Reservoir Storage (1000 AF) - End of April                 |        Watershed Snowpack Analysis - May 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    753.0    719.8    392.0 |   N PLATTE above Northgate    8        99        96
                                                                        |
                                                                        |   ENCAMPMENT RIVER            4        73        73
                                                                        |
                                                                        |   BRUSH CREEK                 5        64        72
                                                                        |
                                                                        |   MEDICINE BOW & ROCK CREEK   3        60        64
                                                                        |
                                                                        |   N PLATTE above Seminoe     20        78        80
                                                                        |
==================================================================================================================================
 * 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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