Upper North Platte River Basin (8)
April 1998

Snow
The 20 snow courses above Seminoe Reservoir average about 87 percent of average snow water equivalent (SWE) recorded for this time of the year (snow depths range from 21 to 61 inches). SWE in the drainage area above Northgate is about 10 percent below average and 67 percent of last year at this time. SWE in the Encampment River drainage is about 88 percent of normal and 71 percent of last year. Brush Creek SWE for the year is about 93 percent of normal and 78 percent of last year's SWE. Medicine Bow and Rock Creek drainage SWE is about 82 percent of average and 70 percent of 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 8 percent above average and about 50 percent more than last year's amount. March precipitation varied from 45 percent of average at Reno Hill SNOTEL to 143 percent of average at North French Creek SNOTEL. Total precipitation, for the water year to date, is 97 percent of average for the basin, which is about 79 percent of last year's amount.

Reservoirs
Seminoe Reservoir is currently storing about 208 percent of normal for this time of the year. Currently the reservoir is storing about 20 percent more than last year. Seminoe Reservoir storage is estimated to be 766,400 acre feet. Last year the reservoir had 640,300 acre feet in storage. The reservoir is currently being drawn down in anticipation of spring runoff

Streamflow
The entire drainage basin is expected to have below average runoff. The April through September 50 percent chance yield for the North Platte River near the Colorado state line is expected to be 225,000 acre feet (83 percent of average). Encampment River near Encampment is estimated to yield 145,000 acre feet (93 percent of normal). North Platte River near Sinclair will yield about 620,000 acre feet (about 86 percent of normal). Rock Creek near Arlington is estimated to yield 48,000 acre feet (about 86 percent of average). Medicine Bow River above Seminoe Reservoir is expected to yield about 85,000 acre feet (about 67 percent of normal). Seminoe Reservoir inflow should be about (705,000 acre feet (83 percent of normal). See the following table for more detailed information on projected runoff. 

==================================================================================================================================
                                                  UPPER NORTH PLATTE RIVER BASIN
                                               Streamflow Forecasts - April 1, 1998
==================================================================================================================================
                                              |  <<====== 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       129       186    |      225        83    |       264       321            271
                                                                    |                       |
Encampment River nr Encampment       APR-SEP       107       130    |      145        93    |       160       183            156
                                                                    |                       |
North Platte River nr Sinclair       APR-SEP       384       525    |      620        86    |       715       856            719
                                                                    |                       |
Rock Creek nr Arlington              APR-SEP        36        43    |       48        86    |        54        62             56
                                                                    |                       |
Medicine Bow River ab Seminoe Reserv APR-SEP        35        62    |       85        67    |       112       157            127
                                                                    |                       |
Seminoe Reservoir Inflow             APR-JUL       402       556    |      660        84    |       764       918            788
                                     APR-SEP       426       592    |      705        83    |       818       984            851
                                                                    |                       |
==================================================================================================================================
                     UPPER NORTH PLATTE RIVER BASIN                     |             UPPER NORTH PLATTE RIVER BASIN
             Reservoir Storage (1000 AF) - End of March                 |        Watershed Snowpack Analysis - April 1, 1998
==================================================================================================================================
                                      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    766.4    640.3    368.0 |   N PLATTE above Northgate    8        72        84
                                                                        |
                                                                        |   ENCAMPMENT RIVER            4        71        88
                                                                        |
                                                                        |   BRUSH CREEK                 5        78        93
                                                                        |
                                                                        |   MEDICINE BOW & ROCK CREEK   3        70        82
                                                                        |
                                                                        |   N PLATTE above Seminoe     20        73        87
                                                                        |
==================================================================================================================================
 * 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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