March 1999 Water Supply Outlook - Lower North Platte River Basin (9)

Lower North Platte River Basin (9)
March 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 99 percent of normal (111 % of last year). The Sweetwater drainage is currently 103 percent of average (146 % of last year). Deer and LaPrele Creeks are 89 percent of average (87 percent of last year). The North Platte above the Laramie River drainage is 100 percent of average (112 % of last year). The Laramie River above the mouth is 95 percent of average (111 % of last year). The Laramie River above Laramie is 96 percent of average (110 % of last year). And, the Little Laramie River is 91 percent of normal (112 percent of last year). For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
Of the 8 reporting stations, percentages for the month range from 52 to 186. February precipitation for the basin was 120 percent of average (135 percent of last year). The water year-to-date precipitation for the basin is currently 136 percent of average (148 percent of last year). Year to date percentages range from 112 to 266.

Reservoir
Lower North Platte River basin reservoir storage is average to well above average. Reservoir storage is as follows: Alcova 157,700 acre feet (100 percent of average); Glendo 450,900 acre feet (118 percent of average); Guernsey 19,400 acre feet (143 percent of average); Pathfinder 916,700 acre feet (155 percent of average); Seminoe 705,200 acre feet (172 percent of average); and Wheatland No. 2 61,000 acre feet (141 percent of average). Water allocated to project use is also above average with North Platte Project users at 144 percent of average, Kendrick Project users at 120 percent of average, and Glendo Project users at 126 percent of average.

Streamflow
Yields from 60 to 119 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 88,000 acre-feet (119 percent of average). Deer Creek at Glenrock is expected to yield about 64 percent of average (25,000 acre-feet). LaPrele Creek above the reservoir is estimated to yield 60 percent of average (14,900 acre-feet). North Platte River below Guernsey Reservoir is expected to yield about 96 percent of normal (949,000 acre-feet), and below Glendo Reservoir is anticipated to yield about 95 percent of average (911,000 acre-feet). Laramie River near Woods should yield about 102 percent of average (138,000 acre-feet). The Little Laramie near Filmore should produce about 56,000 acre-feet (88 percent of average).

==================================================================================================================================
                                      LOWER NORTH PLATTE, SWEETWATER & LARAMIE RIVER BASINS
                                               Streamflow Forecasts - March 1, 1999
==================================================================================================================================
                                              |  <<====== 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        40        65    |       82       119    |        99       125             69
                                     APR-SEP        44        70    |       88       119    |       106       132             74
                                                                    |                       |
Deer Creek at Glenrock               APR-SEP      10.3      18.3    |       25        64    |        33        46             39
                                                                    |                       |
La Prele Creek ab La Prele Reservoir APR-JUL       2.4       8.1    |     14.9        60    |        25        46             25
                                                                    |                       |
North Platte River blw Glendo        APR-SEP       539              |      911        95    |                1396            963
                                                                    |                       |
North Platte River blw Guernsey      APR-SEP       564              |      949        96    |                1454            989
                                                                    |                       |
Laramie River nr Woods               APR-SEP        72       111    |      138       102    |       165       204            135
                                                                    |                       |
Little Laramie River nr Filmore      APR-SEP        35        48    |       56        88    |        64        77             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, 1999
==================================================================================================================================
                                      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    157.7    157.6    157.1 |   SWEETWATER                  3       146       103
                                                                        |
GLENDO                                 506.4    450.9    447.9    383.1 |   DEER & LaPRELE CREEKS       4        87        89
                                                                        |
GUERNSEY                                45.6     19.4     24.3     13.6 |   N PLATTE abv Laramie R.    27       112       100
                                                                        |
PATHFINDER                            1016.5    916.7    971.4    590.0 |   LARAMIE RIVER abv Laramie   8       110        96
                                                                        |
SEMINOE                               1016.7    705.2    837.5    409.0 |   LITTLE LARAMIE RIVER        4       112        91
                                                                        |
WHEATLAND #2                            98.9     61.0     63.0     43.2 |   LARAMIE RIVER above mouth  11       111        95
                                                                        |
NORTH PLATTE PROJ                     1062.1    910.2   1030.2    633.3 |   NORTH PLATTE               34       111        99
                                                                        |
KENDRICK PROJECT                      1201.7    979.1   1006.7    818.1 |
                                                                        |
GLENDO PROJECT USERS                   183.2    159.3    158.1    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.
(D) - The operational measurement of flow at this point has been discountinued.

To March 1999 Basin Outlook Report Contents Page

Lower North Platte River Basin (9) March 1999

Lower North Platte River Basin (9)
March 1999