Upper North Platte River Basin (8)
April 2000

Snow
The snow courses above Seminoe Reservoir have about 89 percent of average snow water equivalent (SWE) recorded for this time of the year (104 percent of last year). SWE in the drainage area above Northgate is about 105 percent of average and 121 percent of last year at this time. SWE in the Encampment River drainage is about 80 percent of normal and 95 percent of last year. Brush Creek SWE for the year is about 83 percent of normal and 92 percent of last year's SWE. Medicine Bow and Rock Creek drainage SWE is about 68 percent of average and 89 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 March precipitation was 88 percent of average and about 162 percent of last year's amount. March precipitation varied from 60 percent of average at Reno Hill SNOTEL to 161 percent of average at Wamsutter. Total water-year-to-date precipitation is about 88 percent of average for the basin, which is about 80 percent of last year's amount. Year to date percentage ranges from 64 to 117 percent of average for the 8 reporting stations.

Reservoirs
Seminoe Reservoir is currently storing about 202 percent of normal for this time of the year. Currently, the reservoir is storing 110 percent of last year's amount. Currently, Seminoe Reservoir storage is estimated to be storing 743,000 acre-feet (73 percent of capacity). Last year, at this time, the reservoir had 673,800 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 282,000 acre-feet (104 percent of average). Encampment River near Encampment is estimated to yield 117,000 acre-feet (75 percent of normal). North Platte River near Sinclair will yield about 656,000 acre-feet (91 percent of normal). Rock Creek near Arlington is estimated to yield 38,000 acre-feet (68 percent of average). Medicine Bow River above Seminoe Reservoir is expected to yield about 70,000 acre-feet (55 percent of normal). Seminoe Reservoir inflow should be about (731,000 acre-feet (86 percent of normal). See the following table for more detailed information on projected runoff. 

==================================================================================================================================
                                                  UPPER NORTH PLATTE RIVER BASIN
                                               Streamflow Forecasts - April 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      APR-SEP       184       242    |      282       104    |       322       380            271
                                                                    |                       |
Encampment River nr Encampment       APR-SEP        79       102    |      117        75    |       132       155            156
                                                                    |                       |
North Platte River nr Sinclair       APR-SEP       420       561    |      656        91    |       751       892            719
                                                                    |                       |
Rock Creek nr Arlington              APR-SEP        27        33    |       38        68    |        43        51             56
                                                                    |                       |
Medicine Bow River ab Seminoe Reserv APR-SEP        25        49    |       70        55    |        94       137            127
                                                                    |                       |
Seminoe Reservoir inflow             APR-JUL       415       569    |      673        85    |       777       931            788
                                     APR-SEP       452       618    |      731        86    |       844      1010            851
                                                                    |                       |
==================================================================================================================================
                     UPPER NORTH PLATTE RIVER BASIN                     |             UPPER NORTH PLATTE RIVER BASIN
             Reservoir Storage (1000 AF) - End of March                 |        Watershed Snowpack Analysis - April 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    743.0    673.8    368.0 |   N PLATTE above Northgate    8       121       105
                                                                        |
                                                                        |   ENCAMPMENT RIVER            1        83        96
                                                                        |
                                                                        |   BRUSH CREEK                 3        95        77
                                                                        |
                                                                        |   MEDICINE BOW & ROCK CREEK   1       103        63
                                                                        |
                                                                        |   N PLATTE above Seminoe     12       113        98
                                                                        |
==================================================================================================================================
 * 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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