Upper North Platte River Basin (8)
April 2001

Snow
The snow courses above Seminoe Reservoir have about 77 percent of average snow water equivalent (SWE) recorded for this time of the year (87 percent of last year). SWE in the drainage area above Northgate is about 80 percent of average and 77 percent of last year at this time. SWE in the Encampment River drainage is about 72 percent of normal and 90 percent of last year. Brush Creek SWE for the year is about 82 percent of normal and 99 percent of last year's SWE. Medicine Bow and Rock Creek drainage SWE is about 68 percent of average and 100 percent of last year at this time. For more information see Basin Summary of Snow Courses at the beginning of this report.

Precipitation
Nine reporting stations indicate March precipitation was 69 percent of average and about 78 percent of last year's amount. March precipitation varied from 24 to 89 percent of average. Total water-year-to-date precipitation is about 78 percent of average for the basin, which is about 89 percent of last year's amount. Year to date percentage ranges from 50 to 100 percent of average for the 9 reporting stations.

Reservoirs
Seminoe Reservoir usable storage is currently about 176 percent of normal for this time of the year. The reservoir is storing 87 percent of last year's amount. Seminoe Reservoir is estimated to be storing 646,200 acre- feet (64 percent of capacity). Last year, at this time, the reservoir had 743,000 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 146,000 acre-feet (54 percent of average). Encampment River near Encampment is estimated to yield 111,000 acre-feet (71 percent of normal). Rock Creek near Arlington is estimated to yield 35,000 acre-feet (63 percent of average). Seminoe Reservoir inflow should be about (488,000 acre-feet (57 percent of normal). See the following table for more detailed information on projected runoff. 

==================================================================================================================================
                                                  UPPER NORTH PLATTE RIVER BASIN
                                               Streamflow Forecasts - April 1, 2001
==================================================================================================================================
                                              |  <<====== 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        48       106    |      146        54    |       186       244            271
                                                                    |                       |
Encampment River nr Encampment       APR-SEP        73        96    |      111        71    |       126       149            156
                                                                    |                       |
Rock Creek nr Arlington              APR-SEP        25        31    |       35        63    |        40        47             56
                                                                    |                       |
Seminoe Reservoir inflow             APR-JUL       299       394    |      450        57    |       554       708            788
                                     APR-SEP       236       386    |      488        57    |       590       740            851
                                                                    |                       |
==================================================================================================================================
                     UPPER NORTH PLATTE RIVER BASIN                     |             UPPER NORTH PLATTE RIVER BASIN
             Reservoir Storage (1000 AF) - End of March                 |        Watershed Snowpack Analysis - April 1, 2001
==================================================================================================================================
                                      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    646.2    743.0    368.0 |   N PLATTE above Northgate    7        77        80
                                                                        |
                                                                        |   ENCAMPMENT RIVER            4        90        72
                                                                        |
                                                                        |   BRUSH CREEK                 5        99        82
                                                                        |
                                                                        |   MEDICINE BOW & ROCK CREEK   3       100        68
                                                                        |
                                                                        |   N PLATTE above Seminoe     19        87        77
                                                                        |
==================================================================================================================================
 * 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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