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

Lower North Platte River Basin (9)
March 2000

Snow
SWE for the North Platte River basin in Wyoming averages 90 percent of normal (91 % of last year). The Sweetwater drainage is currently 90 percent of average (90 % of last year). Deer and LaPrele Creeks are currently 94 percent of normal (106 percent of last year). SWE for the North Platte above the Laramie River drainage is 90 percent of average (90 % of last year). SWE for the Laramie River above the mouth is 90 percent of average (95 % of last year). SWE for the Laramie River above Laramie is 94 percent of average (97 % of last year). And SWE in the Little Laramie River is 83 percent of normal (91 % of last year). 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 45 to 211. February precipitation for the basin was 115 percent of average (95 percent of last year). The water year-to-date precipitation for the basin is currently 86 percent of average (67 percent of last year). Year to date percentages range from 56 to 103.

Reservoir
The Lower North Platte River basin reservoir storage is average to well above average. Reservoir storage is as follows: Alcova 156,100 acre feet (99 percent of average); Glendo 381,800 acre feet (100 percent of average); Guernsey 15,900 acre feet (117 percent of average); Pathfinder 960,500 acre feet (163 percent of average); Seminoe 798,200 acre feet (195 percent of average); and Wheatland No.2 70,000 acre feet (162 percent of average). 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 122 percent of average.

Streamflow
Yields from 73 to 86 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 55,000 acre-feet (74 percent of average). Deer Creek at Glenrock is expected to yield about 77 percent of average (30,000 acre-feet). LaPrele Creek above the reservoir is estimated to yield 80 percent of average (20,000 acre-feet). North Platte River below Guernsey Reservoir is expected to yield about 83 percent of normal (816,000 acre-feet), and below Glendo Reservoir is anticipated to yield about 81 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 about 55,000 acre-feet (86 percent of average).

==================================================================================================================================
                                      LOWER NORTH PLATTE, SWEETWATER & LARAMIE RIVER BASINS
                                               Streamflow Forecasts - March 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        26        33    |       50        73    |        67        93             69
                                     APR-SEP        29        37    |       55        74    |        73        99             74
                                                                    |                       |
Deer Creek at Glenrock               APR-SEP      13.6        23    |       30        77    |        39        53             39
                                                                    |                       |
La Prele Creek ab La Prele Reservoir APR-SEP       8.0      11.0    |       20        80    |        26        35             25
                                                                    |                       |
North Platte River blw Glendo        APR-SEP       433              |      784        81    |                1242            963
                                                                    |                       |
North Platte River blw Guernsey      APR-SEP       445              |      816        83    |                1296            989
                                                                    |                       |
Laramie River nr Woods               APR-SEP        44        83    |      110        82    |       137       176            135
                                                                    |                       |
Little Laramie River nr Filmore      APR-SEP        34        47    |       55        86    |        63        76             64
                                                                    |                       |
==================================================================================================================================
          LOWER NORTH PLATTE, SWEETWATER & LARAMIE RIVER BASINS         |  LOWER NORTH PLATTE, SWEETWATER & LARAMIE RIVER BASINS
             Reservoir Storage (1000 AF) - End of February              |        Watershed Snowpack Analysis - March 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    156.1    157.7    157.1 |   SWEETWATER                  3        76        78
                                                                        |
GLENDO                                 506.4    381.8    450.9    383.1 |   DEER & LaPRELE CREEKS       4       106        94
                                                                        |
GUERNSEY                                45.6     15.9     19.4     13.6 |   N PLATTE abv Laramie R.    27        90        90
                                                                        |
PATHFINDER                            1016.5    960.5    916.7    590.0 |   LARAMIE RIVER abv Laramie   8        97        94
                                                                        |
SEMINOE                               1016.7    798.2    705.2    409.0 |   LITTLE LARAMIE RIVER        4        91        83
                                                                        |
WHEATLAND #2                            98.9     70.0     61.0     43.2 |   LARAMIE RIVER above mouth  11        95        90
                                                                        |
NORTH PLATTE PROJ                     1062.1    998.6    910.2    633.3 |   NORTH PLATTE               34        91        90
                                                                        |
KENDRICK PROJECT                      1201.7    989.9    979.1    818.1 |
                                                                        |
GLENDO PROJECT USERS                   183.2    154.7    159.3    126.8 |
                                                                        |
==================================================================================================================================
 * 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.

To March 2000 Basin Outlook Report Contents Page

Lower North Platte River Basin (9) March 2000

Lower North Platte River Basin (9)
March 2000