Lower North Platte River Basin (9)
June 1998

Snow
Most areas in the basin have received less than normal snow for this time of year. The North Platte River in Wyoming averages 67 percent of normal (49 % of last year). The Sweetwater drainage is currently 4 percent of average (5 % of last year). Deer and LaPrele Creeks are melted out. The North Platte above the Laramie River drainage is 68 percent of average (50 % of last year). The Laramie River above the mouth is 41 percent of average (32 % of last year). The Little Laramie River above Laramie is 45 percent of average (37 % of last year). For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
Of the 20 reporting stations percentages for the month range from 21 at LaPrele Creek to 131 at Wheatland. May precipitation for the basin was 69 percent of average (59 percent of last year). The water year-to-date precipitation for the basin is currently 85 percent of average (71 percent of last year).

Reservoir
Lower North Platte River basin reservoir storage is above average. Storage at all of the reservoirs is near average to well above average. Reservoir storage is as follows: Alcova 180,500 acre feet (100 percent of average); Glendo 467,300 acre feet (93 percent of average); Guernsey 34,100 acre feet (99 percent of average); Pathfinder 971,200 acre feet (152 percent of average); Seminoe 777,200 acre feet (141 percent of average); and Wheatland No. Two 71,000 acre feet (130 percent of average). Water allocated to project use is also above average with North Platte Project users at 116 percent of average, Kendrick Project users at 123 percent of average, and Glendo Project users at 112 percent of average.

Streamflow Below average yields are expected over the entire 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 31,000 acre feet (86 percent of average). Deer Creek at Glenrock is expected to yield 11 percent of average (800 acre feet). LaPrele Creek above the reservoir should yield 10 percent of average (600 acre feet). Laramie River near Woods should yield about 47 percent of average (42,000 acre feet). The Little Laramie near Filmore should produce 34,000 acre feet (71 percent of average). 

==================================================================================================================================
                                      LOWER NORTH PLATTE, SWEETWATER & LARAMIE RIVER BASINS
                                               Streamflow Forecasts - June 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)
====================================================================|=======================|=====================================
Sweetwater River nr Alcova           JUN-JUL      16.0        22    |       26        84    |        30        36             31
                                     JUN-SEP      18.4        26    |       31        86    |        36        44             36
                                                                    |                       |
Deer Creek at Glenrock               JUN-SEP      0.01      0.32    |     0.80        11    |      1.49      2.88           7.25
                                                                    |                       |
La Prele Creek ab La Prele Reservoir JUN-SEP      0.04      0.26    |     0.60        10    |      1.15      2.46           6.20
                                                                    |                       |
Laramie River nr Woods               JUN-SEP      12.8        30    |       42        47    |        54        71             89
                                                                    |                       |
Little Laramie River nr Filmore      JUN-SEP        25        31    |       34        71    |        38        43             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, 1998
==================================================================================================================================
                                      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    180.5    180.3    180.4 |   SWEETWATER                  1         5         4
                                                                        |
GLENDO                                 506.4    467.3    507.7    501.0 |   DEER & LaPRELE CREEKS       2         0         0
                                                                        |
GUERNSEY                                45.6     34.1     35.1     34.5 |   N PLATTE abv Laramie R.    16        50        68
                                                                        |
PATHFINDER                            1016.5    971.2    956.3    638.0 |   LARAMIE RIVER abv Laramie   3        37        45
                                                                        |
SEMINOE                               1016.7    777.2    785.4    551.0 |   LITTLE LARAMIE RIVER        1        23        32
                                                                        |
WHEATLAND #2                            98.9     71.0     63.0     54.6 |   LARAMIE RIVER above mouth   4        32        41
                                                                        |
NORTH PLATTE PROJ                     1062.1   1056.8   1052.9    909.8 |   NORTH PLATTE               17        49        67
                                                                        |
KENDRICK PROJECT                      1201.7   1037.6   1022.0    844.4 |
                                                                        |
GLENDO PROJECT USERS                   183.2    167.1    164.6    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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