Lower North Platte River Basin (9)
June 2000

Snow
SWE for the North Platte River basin in Wyoming averages 34 percent of normal (27 % of last year). The Sweetwater drainage is melted out as of June 1. Deer and LaPrele Creeks are also melted out. SWE for the North Platte above the Laramie River drainage is 34 percent of average (27 % of last year). SWE for the Laramie River above the mouth is 26 percent of average (22 % of last year). SWE for the Laramie River above Laramie is 35 percent of average (32 % of last year). The Little Laramie River is melted out.. For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
Of the 6 reporting stations, percentages for the month range from 35 to 285. May precipitation for the basin was 127 percent of average (125 percent of last year). The water year-to-date precipitation for the basin is currently 97 percent of average (79 percent of last year). Year to date percentages range from 70 to 132.

Reservoir
The Lower North Platte River basin reservoir storage is average to well above average. Reservoir storage is as follows: Alcova 180,700 acre feet (100 percent of average); Glendo 507,100 acre feet (101 percent of average); Guernsey 35,900 acre feet (104 percent of average); Pathfinder 993,100 acre feet (156 percent of average); Seminoe 914,200 acre feet (166 percent of average); and Wheatland No.2 81,000 acre feet (148 percent of average). Water allocated to project use is also above average with North Platte Project users at 117 percent of average, Kendrick Project users at 124 percent of average, and Glendo Project users at 115 percent of average.

Streamflow
Yields from 37 to 99 percent are expected in the basin during the forecast period. The following yields are based on the fifty percent chance probability runoff for the June through September forecast period. The Sweetwater near Alcova is forecast to yield about 15,800 acre-feet (44 percent of average). Deer Creek at Glenrock is expected to yield about 99 percent of average (7,200 acre-feet). LaPrele Creek above the reservoir is estimated to yield 79 percent of average (4,900 acre-feet). North Platte River below Guernsey Reservoir is expected to yield about 64 percent of normal (306,000 acre-feet), and below Glendo Reservoir is anticipated to yield about 68 percent of average (315,000 acre-feet). Laramie River near Woods should yield about 88 percent of average (78,000 acre-feet). The Little Laramie near Filmore should produce about 21,000 acre-feet (44 percent of average).

 
==================================================================================================================================
                                      LOWER NORTH PLATTE, SWEETWATER & LARAMIE RIVER BASINS
                                               Streamflow Forecasts - June 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)
====================================================================|=======================|=====================================
Sweetwater River nr Alcova           JUN-JUL       4.7       7.5    |     11.6        37    |      15.7        22             31
                                     JUN-SEP       6.5      10.7    |     15.8        44    |        21        28             36
                                                                    |                       |
Deer Creek at Glenrock               JUN-SEP      3.53      5.56    |     7.20        99    |      9.05     12.16           7.25
                                                                    |                       |
La Prele Creek ab La Prele Reservoir JUN-SEP      1.69      3.33    |     4.90        79    |      6.90     10.73           6.20
                                                                    |                       |
North Platte River blw Glendo        JUN-SEP       255              |      315        68    |                 422            464
                                                                    |                       |
North Platte River blw Guernsey      JUN-SEP       248              |      306        64    |                 409            476
                                                                    |                       |
Laramie River nr Woods               JUN-SEP        49        66    |       78        88    |        90       107             89
                                                                    |                       |
Little Laramie River nr Filmore      JUN-SEP      12.3      17.5    |       21        44    |        25        30             48
                                                                    |                       |
==================================================================================================================================
          LOWER NORTH PLATTE, SWEETWATER & LARAMIE RIVER BASINS         |  LOWER NORTH PLATTE, SWEETWATER & LARAMIE RIVER BASINS
             Reservoir Storage (1000 AF) - End of May                   |        Watershed Snowpack Analysis - June 1, 2000
==================================================================================================================================
                                      Usable |  *** Usable Storage ***  |                            Number     This Year as % of
Reservoir                            Capacity|  This      Last          |   Watershed                  of       =================
                                             |  Year      Year     Avg  |                          Data Sites   Last Yr   Average
========================================================================|=========================================================
ALCOVA                                 184.3    180.7    179.1    180.4 |   SWEETWATER                  1         1         0
                                                                        |
GLENDO                                 506.4    507.1    553.4    501.0 |   DEER & LaPRELE CREEKS       2         0         0
                                                                        |
GUERNSEY                                45.6     35.9     33.8     34.5 |   N PLATTE abv Laramie R.    16        25        34
                                                                        |
PATHFINDER                            1016.5    993.1    993.3    638.0 |   LARAMIE RIVER abv Laramie   3        32        35
                                                                        |
SEMINOE                               1016.7    914.2    842.9    551.0 |   LITTLE LARAMIE RIVER        1         0         0
                                                                        |
WHEATLAND #2                            98.9     81.0     90.0     54.6 |   LARAMIE RIVER above mouth   4        22        26
                                                                        |
NORTH PLATTE PROJ                     1062.1   1061.5   1061.5    909.8 |   NORTH PLATTE               17        27        34
                                                                        |
KENDRICK PROJECT                      1201.7   1047.4   1047.4    844.4 |
                                                                        |
GLENDO PROJECT USERS                   183.2    172.2    172.2    149.7 |
                                                                        |
==================================================================================================================================
 * 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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