May 1998 Water Supply Outlook - Lower North Platte River Basin (9)

Lower North Platte River Basin (9)
May 1998

Snow
Most areas in the basin have received less than normal snow for this time of year. The North Platte River in Wyoming averages 88 percent of normal (66 % of last year). The Sweetwater drainage is currently 86 percent of average (58 % of last year). Deer and LaPrele Creeks are currently at 77 percent of average (44 % of last year). The North Platte above the Laramie River drainage is 87 percent of average (64 % of last year). The Laramie River above the mouth is 90 percent of average (71 % of last year). The Little Laramie River above Laramie is 90 percent of average (70 % of last year). For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
Of the 20 reporting stations, Albin had the smallest percentage of average (0 percent) for the month. Carpenter 3E reported the largest percentage of average (134 percent of the April average). April precipitation for the basin was 71 percent of average (65 percent of last year). The water year-to-date precipitation for the basin is currently 88 percent of average (72 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 179,600 acre feet (100 percent of average); Glendo 473,700 acre feet (104 percent of average); Guernsey 31,700 acre feet (97 percent of average); Pathfinder 982,300 acre feet (161 percent of average); Seminoe 690,400 acre feet (176 percent of average); and Wheatland No. Two 79,000 acre feet (144 percent of average). Water allocated to project use is also above average with North Platte Project users at 140 percent of average, Kendrick Project users at 119 percent of average, and Glendo Project users at 130 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 May through September forecast period. The Sweetwater near Alcova is forecast to yield 67,000 acre feet (110 percent of average). Deer Creek at Glenrock is expected to yield 24 percent of average (7,100 acre feet). LaPrele Creek above the reservoir should yield 33 percent of average (6,500 acre feet). North Platte River below Glendo should yield about 80 percent of average (640,000 acre feet). Below Guernsey, the North Platte River should yield near 81 percent of average (670,000 acre feet). Laramie River near Woods should yield about 89 percent of average (113,000 acre feet). The Little Laramie near Filmore should produce 59,000 acre feet (97 percent of average).


==================================================================================================================================
                                      LOWER NORTH PLATTE, SWEETWATER & LARAMIE RIVER BASINS
                                               Streamflow Forecasts - May 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           MAY-JUL        38        52    |       61       109    |        70        84             56
                                     MAY-SEP        42        57    |       67       110    |        77        92             61
                                                                    |                       |
Deer Creek at Glenrock               MAY-SEP       3.5       5.5    |      7.1        24    |       8.9      12.0             30
                                                                    |                       |
La Prele Creek ab La Prele Reservoir MAY-SEP       1.3       3.7    |      6.5        33    |      10.4      18.4             20
                                                                    |                       |
NORTH PLATTE RIVER blw Glendo        MAY-SEP       487              |      640        80    |                 895            799
                                                                    |                       |
NORTH PLATTE R. blw Guernsey         MAY-SEP       510              |      670        81    |                 938            823
                                                                    |                       |
Laramie River nr Woods               MAY-SEP        68        95    |      113        89    |       131       158            127
                                                                    |                       |
Little Laramie River nr Filmore      MAY-SEP        50        55    |       59        97    |        63        69             61
                                                                    |                       |
==================================================================================================================================
          LOWER NORTH PLATTE, SWEETWATER & LARAMIE RIVER BASINS         |  LOWER NORTH PLATTE, SWEETWATER & LARAMIE RIVER BASINS
             Reservoir Storage (1000 AF) - End of April                 |        Watershed Snowpack Analysis - May 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    179.6    180.7    179.9 |   SWEETWATER                  3        58        86
                                                                        |
GLENDO                                 506.4    473.7    488.1    457.6 |   DEER & LaPRELE CREEKS       3        40        72
                                                                        |
GUERNSEY                                45.6     31.7     31.0     32.8 |   N PLATTE abv Laramie R.    26        64        87
                                                                        |
PATHFINDER                            1016.5    982.3    922.2    609.0 |   LARAMIE RIVER abv Laramie   9        71        90
                                                                        |
SEMINOE                               1016.7    690.4    611.0    392.0 |   LITTLE LARAMIE RIVER        4        70        90
                                                                        |
WHEATLAND #2                            98.9     79.0     71.0     54.9 |   LARAMIE RIVER above mouth  12        69        89
                                                                        |
NORTH PLATTE PROJ                     1062.1   1102.6   1047.3    786.7 |   NORTH PLATTE               34        66        88
                                                                        |
KENDRICK PROJECT                      1201.7    959.3    819.4    807.0 |
                                                                        |
GLENDO PROJECT USERS                   183.2    167.0    167.2    128.9 |
                                                                        |
==================================================================================================================================
 * 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 May 1998 Basin Outlook Report Contents Page

Lower North Platte River Basin (9) May 1998

Lower North Platte River Basin (9)
May 1998