Lower North Platte River Basin (9)
April 1998

Snow
Most areas in the basin have received less than normal snow for this time of year. The Lower North Platte River averages 85 percent of normal (71 % of last year). Deer and LaPrele Creeks are currently at 86 percent of average (63 % of last year). The Sweetwater drainage is currently 79 percent (55 % of last year). The North Platte above the Laramie River drainage is 86 percent of average (70 % of last year). The Little Laramie River above Laramie is 81 percent of average (71 % of last year). The Laramie River above the mouth is 81 percent of average (75 % of last year). For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
Of the 20 reporting stations, Reno Hill SNOTEL had smallest percentage of average (45 percent) for the month. Muddy Gap reported the largest percentage of average (500 percent of the March average). March precipitation for the basin was 98 percent of average (159 percent of last year). The water year-to-date precipitation for the basin is currently 94 percent of average (76 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 159,200 acre feet (98 percent of average); Glendo 450,900 acre feet (107 percent of average); Guernsey 31,300 acre feet (145 percent of average); Pathfinder 995,700 acre feet (161 percent of average); Seminoe 766,400 acre feet (208 percent of average); and Wheatland No. Two 70,000 acre feet (144 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 60,000 acre feet (81 percent of average). Deer Creek at Glenrock is expected to flow at 64 percent of average (25,000 acre feet). LaPrele Creek above the reservoir should yield 50 percent of average (12,500 acre feet). North Platte River below Glendo should yield about 78 percent of average (753,000 acre feet). Below Guernsey, the North Platte River should yield near 79 percent of average (784,000 acre feet). Laramie River near Woods should yield about 82 percent of average (110,000 acre feet). The Little Laramie near Filmore should produce 55,000 acre feet (86 percent of average). 

==================================================================================================================================
                                      LOWER NORTH PLATTE, SWEETWATER & LARAMIE RIVER BASINS
                                               Streamflow Forecasts - April 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           APR-JUL      15.5        39    |       55        80    |        71        95             69
                                     APR-SEP      19.1        44    |       60        81    |        77       101             74
                                                                    |                       |
Deer Creek at Glenrock               APR-SEP      12.2      19.3    |       25        64    |        31        42             39
                                                                    |                       |
La Prele Creek ab La Prele Reservoir APR-SEP       2.6       7.3    |     12.5        50    |      19.7        35             25
                                                                    |                       |
NORTH PLATTE RIVER blw Glendo        APR-SEP       443              |      753        78    |                1079            963
                                                                    |                       |
NORTH PLATTE R. blw Guernsey         APR-SEP       465              |      784        79    |                1118            989
                                                                    |                       |
Laramie River nr Woods               APR-SEP        47        84    |      110        82    |       136       173            135
                                                                    |                       |
Little Laramie River nr Filmore      APR-SEP        38        48    |       55        86    |        62        72             64
                                                                    |                       |
==================================================================================================================================
          LOWER NORTH PLATTE, SWEETWATER & LARAMIE RIVER BASINS         |  LOWER NORTH PLATTE, SWEETWATER & LARAMIE RIVER BASINS
             Reservoir Storage (1000 AF) - End of March                 |        Watershed Snowpack Analysis - April 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    159.2    157.0    162.0 |   SWEETWATER                  4        55        79
                                                                        |
GLENDO                                 506.4    450.9    482.2    420.3 |   DEER & LaPRELE CREEKS       4        63        86
                                                                        |
GUERNSEY                                45.6     31.3     28.7     21.6 |   N PLATTE abv Laramie R.    28        70        86
                                                                        |
PATHFINDER                            1016.5    995.7    905.0    619.0 |   LARAMIE RIVER abv Laramie   9        79        82
                                                                        |
SEMINOE                               1016.7    766.4    640.3    368.0 |   LITTLE LARAMIE RIVER        4        71        81
                                                                        |
WHEATLAND #2                            98.9     70.0     62.0     48.7 |   LARAMIE RIVER above mouth  12        75        81
                                                                        |
NORTH PLATTE PROJ                     1062.1   1077.3    916.7    676.0 |   NORTH PLATTE               36        71        85
                                                                        |
KENDRICK PROJECT                      1201.7    939.6    924.8    812.7 |
                                                                        |
GLENDO PROJECT USERS                   183.2    168.6    168.5    127.2 |
                                                                        |
==================================================================================================================================
 * 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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