Upper North Platte River Basin
March 1997

Snow
The 21 snow courses above Seminoe Reservoir average about 39 percent more than the normal Snow Water Equivalent (SWE) recorded for this time of the year. In Colorado (above Northgate), SWE is about 35 percent above average and 3 percent less than last year at this time. SWE in the Encampment River drainage is about 45 percent more than normal and 25 percent more than last year. Brush Creek SWE for the year is about 46 percent more than normal and 32 percent more than last year. The Medicine Bow and Rock Creek drainage SWE is about 35 percent above average and 28 percent above last year at this time. The following graph demonstrates that current SWE is above maximum recorded levels. For more information see Basin Summary of Snow Courses at the beginning of this report.

Precipitation
Twelve reporting stations indicate February precipitation was 29 percent below average. February precipitation was about 22 percent less than last year's amount. Total precipitation, for the water year to date, is 33 percent more than average for the basin. Total precipitation for the water year is about 17 percent more than last year's amount.

Reservoirs
Seminoe Reservoir is currently storing about 64 percent more than normal for this time of the year; currently the reservoir is storing about 8 percent less than last year's storage. Seminoe Reservoir storage is estimated to be about 671,700 acre feet; last year the reservoir had 732,500 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 455,000 acre feet (about 68 percent more than normal); the Encampment River near Encampment is estimated to yield 224,000 acre feet for (44 percent above normal); the North Platte River near Sinclair will yield about 1,097,000 acre feet (about 53 percent above normal); Rock Creek near Arlington is estimated to yield 74,000 acre feet (about 28 percent above average); Medicine Bow River near Hanna is expected to yield about 185,000 acre feet (about 46 percent above normal). Seminoe Reservoir inflow is estimated to be 1,190,000 acre feet (49 percent above normal). See the following table for more detailed information on projected runoff. 

==================================================================================================================================
                                                  UPPER NORTH PLATTE RIVER BASIN
                                               Streamflow Forecasts - March 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       379       412    |      455       168    |       498       531            271
                                                                    |                       |
ENCAMPMENT RIVER near Encampment     APR-SEP       183       205    |      224       144    |       243       268            156
                                                                    |                       |
NORTH PLATTE RIVER near Sinclair     APR-SEP       919      1007    |     1097       153    |      1187      1271            718
                                                                    |                       |
ROCK CREEK nr Arlington              APR-SEP        53        66    |       74       128    |        83        95             58
                                                                    |                       |
MEDICINE BOW RIVER nr Hanna          APR-SEP        91       147    |      185       146    |       223       279            127
                                                                    |                       |
SEMINOE RESERVOIR INFLOW             APR-JUL       934      1086    |     1190       149    |      1294      1446            800
                                                                    |                       |
==================================================================================================================================
                     UPPER NORTH PLATTE RIVER BASIN                     |             UPPER NORTH PLATTE RIVER BASIN
             Reservoir Storage (1000 AF) - End of February              |        Watershed Snowpack Analysis - March 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    671.7    732.5    409.0 |   N PLATTE above Northgate    8        97       135
                                                                        |
                                                                        |   ENCAMPMENT RIVER            4       125       145
                                                                        |
                                                                        |   BRUSH CREEK                 5       132       146
                                                                        |
                                                                        |   MEDICINE BOW & ROCK CREEK   3       128       135
                                                                        |
                                                                        |   N PLATTE above Seminoe     20       114       139
                                                                        |
==================================================================================================================================
 * 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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