January 2000 Water Supply Outlook - Lower North Platte River Basin (9)

Lower North Platte River Basin
January 2000

Snow
SWE for the North Platte River basin in Wyoming averages 63 percent of normal (87 % of last year). The Sweetwater drainage is currently 39 percent of average (46 % of last year). Deer and LaPrele Creeks are currently 79 percent of normal (137 percent of last year). SWE for the North Platte above the Laramie River drainage is 64 percent of average (91 % of last year). SWE for the Laramie River above the mouth is 55 percent of average (71 % of last year). SWE for the Laramie River above Laramie is 59 percent of average (68 % of last year). And SWE in the Little Laramie River is 47 percent of normal (81 % of last year). For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
Of the 12 reporting stations, percentages for the month range from 4 to 144. December precipitation for the basin was 80 percent of average (108 percent of last year). The water year-to-date precipitation for the basin is currently 58 percent of average (44 percent of last year). Year to date percentages range from 13 to 85.

Reservoir
The Lower North Platte River basin reservoir storage is average to well above average. Reservoir storage is as follows: Alcova 156,800 acre feet (102 percent of average); Glendo 276,400 acre feet (100 percent of average); Guernsey 10,500 acre feet (191 percent of average); Pathfinder 928,900 acre feet (184 percent of average); Seminoe 845,600 acre feet (156 percent of average); and Wheatland No.2 65,000 acre feet (average not established). Water allocated to project use is also above average with North Platte Project users at 158 percent of average, Kendrick Project users at 121 percent of average, and Glendo Project users at 134 percent of average.

Streamflow
Yields from 28 to 72 percent are expected in the 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 about 21,000 acre-feet (28 percent of average). Deer Creek at Glenrock is expected to yield about 45 percent of average (17,500 acre-feet). LaPrele Creek above the reservoir is estimated to yield 44 percent of average (10,900 acre-feet). North Platte River below Guernsey Reservoir is expected to yield about 46 percent of normal (445,000 acre-feet), and below Glendo Reservoir is anticipated to yield about 47 percent of average (465,000 acre-feet). Laramie River near Woods should yield about 59 percent of average (80,000 acre-feet). The Little Laramie near Filmore should produce about 46,000 acre-feet (72 percent of average).

==================================================================================================================================
                                      LOWER NORTH PLATTE, SWEETWATER & LARAMIE RIVER BASINS
                                               Streamflow Forecasts - January 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           APR-JUL       6.9      11.7    |     18.0        26    |        35        59             69
                                     APR-SEP       7.4      12.6    |       21        28    |        38        63             74
                                                                    |                       |
Deer Creek at Glenrock               APR-SEP       3.9      10.8    |     17.5        45    |        26        41             39
                                                                    |                       |
La Prele Creek ab La Prele Reservoir APR-SEP       1.0       5.2    |     10.9        44    |      19.8        40             25
                                                                    |                       |
North Platte River blw Glendo        APR-SEP       173              |      445        46    |                 847            963
                                                                    |                       |
North Platte River blw Guernsey      APR-SEP       178              |      465        47    |                 880            989
                                                                    |                       |
Laramie River nr Woods               APR-SEP      10.0        52    |       80        59    |       108       150            135
                                                                    |                       |
Little Laramie River nr Filmore      APR-SEP        22        36    |       46        72    |        56        70             64
                                                                    |                       |
==================================================================================================================================
          LOWER NORTH PLATTE, SWEETWATER & LARAMIE RIVER BASINS         |  LOWER NORTH PLATTE, SWEETWATER & LARAMIE RIVER BASINS
             Reservoir Storage (1000 AF) - End of December              |        Watershed Snowpack Analysis - January 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    156.8    156.5    153.1 |   SWEETWATER                  1        46        39
                                                                        |
GLENDO                                 506.4    276.4    347.8    276.4 |   DEER & LaPRELE CREEKS       2       137        79
                                                                        |
GUERNSEY                                45.6     10.5     14.3      5.5 |   N PLATTE abv Laramie R.    16        91        64
                                                                        |
PATHFINDER                            1016.5    928.9    869.8    505.0 |   LARAMIE RIVER abv Laramie   3        68        59
                                                                        |
SEMINOE                               1016.7    845.6    756.7    542.0 |   LITTLE LARAMIE RIVER        1        81        47
                                                                        |
WHEATLAND #2                            98.9     65.0     65.0      --- |   LARAMIE RIVER above mouth   4        71        55
                                                                        |
NORTH PLATTE PROJ                     1062.1    899.1    807.8    568.4 |   NORTH PLATTE               17        87        63
                                                                        |
KENDRICK PROJECT                      1201.7    993.6    982.9    819.8 |
                                                                        |
GLENDO PROJECT USERS                   183.2    155.6    156.5    116.2 |
                                                                        |
==================================================================================================================================
 * 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.
(3) - Forecasts produced in cooperation with Alberta Forecasting Staff Canada

To January 2000 Basin Outlook Report Contents Page

Lower North Platte River Basin January 2000

Lower North Platte River Basin
January 2000