Lower North Platte River Basin (9)
January 1999

Snow
Most areas in the basin have received less than normal snow for this time of year. The North Platte River in Wyoming averages 73 percent of normal (106% of last year). The Sweetwater drainage is currently 84 percent of average (123% of last year). Deer and LaPrele Creeks are 58 percent of average (62 percent of last year). The North Platte above the Laramie River drainage is 71 percent of average (106% of last year). The Laramie River above the mouth is 77 percent of average (103% of last year). The Laramie River above Laramie is 86 percent of average (101% of last year). And the Little Laramie River is 58 percent of normal (108 percent of last year). For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
Of the 21 reporting stations, percentages for the month range from 13 to 247. December precipitation for the basin was 72 percent of average (74 percent of last year). The water year-to-date precipitation for the basin is currently 156 percent of average (171 percent of last year). Year to date percentages range from 71 to 281.

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 156,500 acre feet (102 percent of average); Glendo 347,800 acre feet (126 percent of average); Guernsey 14,300 acre feet (260 percent of average); Pathfinder 869,800 acre feet (172 percent of average); Seminoe 756,700 acre feet (140 percent of average); and Wheatland No. Two average is not established. Current storage in Wheatland #2 is 65,000 acre feet. Water allocated to project use is also above average with North Platte Project users at 142 percent of average, Kendrick Project users at 120 percent of average, and Glendo Project users at 135 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 April through September forecast period. The Sweetwater near Alcova is forecast to yield 48,000 acre feet (65 percent of average). Deer Creek at Glenrock is expected to yield 44 percent of average (17,000 acre feet). LaPrele Creek above the reservoir should yield 40 percent of average (10,000 acre feet). Laramie River near Woods should yield about 86 percent of average (116,000 acre feet). The Little Laramie near Filmore should produce 50,000 acre feet (78 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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