Upper North Platte River Basin
April 1997

Snow
The 20 snow courses above Seminoe Reservoir average about 20 percent more than the normal Snow Water Equivalent (SWE) recorded for this time of the year. In Colorado (above Northgate), SWE is about 17 percent above average and 9 percent less than last year at this time. SWE in the Encampment River drainage is about 24 percent more than normal and 15 percent more than last year. Brush Creek SWE for the year is about 20 percent more than normal and 14 percent more than last year. The Medicine Bow and Rock Creek drainage SWE is about 17 percent above average and 16 percent above 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 March precipitation was 16 percent below average. March precipitation was about 17 percent less than last year's amount. Total precipitation, for the water year to date, is 23 percent more than average for the basin. Total precipitation for the water year is about 12 percent more than last year's amount.

Reservoirs
Seminoe Reservoir is currently storing about 74 percent more than normal for this time of the year; currently the reservoir is storing about 3 percent less than last year's storage. Seminoe Reservoir storage is estimated to be about 640,300 acre feet; last year the reservoir had 659,600 acre feet in storage.

Streamflow
The entire drainage basin is expected to have an above average runoff. The 50 percent chance yield for the North Platte River near the Colorado state line is expected to be 345,000 acre feet (about 27 percent more than normal); the Encampment River near Encampment is estimated to yield 210,000 acre feet (35 percent above normal); the North Platte River near Sinclair will yield about 925,000 acre feet (about 29 percent above normal); Rock Creek near Arlington is estimated to yield 65,000 acre feet (about 12 percent above average); Medicine Bow River near Hanna is expected to yield about 160,000 acre feet (about 26 percent above normal). Seminoe Reservoir inflow is estimated to be 1,015,000 acre feet (27 percent above normal). See the following table for more detailed information on projected runoff. 

==================================================================================================================================
                                                  UPPER NORTH PLATTE RIVER BASIN
                                               Streamflow Forecasts - April 1, 1997
==================================================================================================================================
                                              |  <<====== 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 near Northgate    APR-SEP       265       312    |      345       127    |       378       425            271
                                                                    |                       |
ENCAMPMENT RIVER near Encampment     APR-SEP       174       195    |      210       135    |       225       246            156
                                                                    |                       |
NORTH PLATTE RIVER near Sinclair     APR-SEP       696       848    |      925       129    |      1002      1114            718
                                                                    |                       |
ROCK CREEK nr Arlington              APR-SEP        52        60    |       65       112    |        70        78             58
                                                                    |                       |
MEDICINE BOW RIVER nr Hanna          APR-SEP       118       143    |      160       126    |       177       202            127
                                                                    |                       |
SEMINOE RESERVOIR INFLOW             APR-JUL       848       947    |     1015       127    |      1083      1182            800
                                                                    |                       |
==================================================================================================================================
                     UPPER NORTH PLATTE RIVER BASIN                     |             UPPER NORTH PLATTE RIVER BASIN
             Reservoir Storage (1000 AF) - End of March                 |        Watershed Snowpack Analysis - April 1, 1997
==================================================================================================================================
                                      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    640.3    659.6    368.0 |   N PLATTE above Northgate    8        91       117
                                                                        |
                                                                        |   ENCAMPMENT RIVER            4       115       124
                                                                        |
                                                                        |   BRUSH CREEK                 5       114       120
                                                                        |
                                                                        |   MEDICINE BOW & ROCK CREEK   3       116       117
                                                                        |
                                                                        |   N PLATTE above Seminoe     20       105       120
                                                                        |
==================================================================================================================================
 * 90%, 70%, 30%, and 10% chances of exceeding are the probabilities that the actual flow 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.
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