Upper North Platte River Basin (8)
April 1999

Snow
The snow courses above Seminoe Reservoir average about 86 percent of average snow water equivalent (SWE) recorded for this time of the year (99 percent of last year). SWE in the drainage area above Northgate is about 86 percent of average and 102 percent of last year at this time. SWE in the Encampment River drainage is about 84 percent of normal and 96 percent of last year. Brush Creek SWE for the year is about 90 percent of normal and 115 percent of last year's SWE. Medicine Bow and Rock Creek drainage SWE is about 76 percent of average and 93 percent of last year at this time. In the North Platte River above Seminoe Reservoir, SWE is about 86 percent of normal (99 percent of last year). For more information see Basin Summary of Snow Courses at the beginning of this report.

Precipitation
Eight reporting stations indicate March precipitation was 54 percent of average and about 55 percent of last year's amount. March precipitation varied from 32 to 78 percent of average. Total water-year-to-date precipitation is about 111 percent of average for the basin, which is about 115 percent of last year's amount. Year to date percentages range from 92 to 137 for the 8 reporting stations.

Reservoirs
Seminoe Reservoir is currently storing about 183 percent of normal for this time of the year. Currently the reservoir is storing 88 percent of last year and 66 percent of capacity. Currently, Seminoe Reservoir storage is estimated to be 673,800 acre-feet. Last year, at this time, the reservoir had 766,400 acre-feet in storage.

Streamflow
The entire drainage basin is expected to have runoff values from 63 to 106 percent of average. 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 220,000 acre-feet (81 percent of average). Encampment River near Encampment is estimated to yield 140,000 acre-feet (90 percent of normal). North Platte River near Sinclair will yield about 600,000 acre-feet (83 percent of normal). Rock Creek near Arlington is estimated to yield 34,000 acre-feet (61 percent of average). Medicine Bow River above Seminoe Reservoir is expected to yield about 44,000 acre-feet (35 percent of normal). Seminoe Reservoir inflow should be about (600,000 acre-feet (76 percent of normal). See the following table for more detailed information on projected runoff. 

==================================================================================================================================
                                                  UPPER NORTH PLATTE RIVER BASIN
                                               Streamflow Forecasts - April 1, 1999
==================================================================================================================================
                                              |  <<====== 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       124       181    |      220        81    |       259       316            271
                                                                    |                       |
Encampment River nr Encampment       APR-SEP       102       125    |      140        90    |       155       178            156
                                                                    |                       |
North Platte River nr Sinclair       APR-SEP       364       505    |      600        83    |       695       836            719
                                                                    |                       |
Rock Creek nr Arlington              APR-SEP        24        30    |       34        61    |        39        46             56
                                                                    |                       |
Medicine Bow River ab Seminoe Reserv APR-SEP      11.0        28    |       44        35    |        64        99            127
                                                                    |                       |
Seminoe Reservoir Inflow             APR-JUL       342       496    |      600        76    |       704       858            788
                                     APR-SEP       371       537    |      650        76    |       763       929            851
                                                                    |                       |
==================================================================================================================================
                     UPPER NORTH PLATTE RIVER BASIN                     |             UPPER NORTH PLATTE RIVER BASIN
             Reservoir Storage (1000 AF) - End of March                 |        Watershed Snowpack Analysis - April 1, 1999
==================================================================================================================================
                                      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    673.8    766.4    368.0 |   N PLATTE above Northgate    8       102        86
                                                                        |
                                                                        |   ENCAMPMENT RIVER            4        95        84
                                                                        |
                                                                        |   BRUSH CREEK                 5        96        90
                                                                        |
                                                                        |   MEDICINE BOW & ROCK CREEK   3        93        76
                                                                        |
                                                                        |   N PLATTE above Seminoe     20        99        86
                                                                        |
==================================================================================================================================
 * 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.
(D) - The operational measurement of flow at this point has been discountinued.
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