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

Lower North Platte River Basin (9)
May 2000

Snow
SWE for the North Platte River basin in Wyoming averages 77 percent of normal (71 % of last year). The Sweetwater drainage is currently 73 percent of average (54 % of last year). Deer and LaPrele Creeks are currently 87 percent of normal (67 percent of last year). SWE for the North Platte above the Laramie River drainage is 80 percent of average (74 % of last year). SWE for the Laramie River above the mouth is 71 percent of average (72 % of last year). SWE for the Laramie River above Laramie is 82 percent of average (82 % of last year). And SWE in the Little Laramie River is 49 percent of normal (48 % 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 29 to 199. April precipitation for the basin was 120 percent of average (62 percent of last year). The water year-to-date precipitation for the basin is currently 92 percent of average (73 percent of last year). Year to date percentages range from 62 to 125.

Reservoir
The Lower North Platte River basin reservoir storage is average to well above average. Reservoir storage is as follows: Alcova 197,700 acre feet (110 percent of average); Glendo 516,100 acre feet (113 percent of average); Guernsey 36,000 acre feet (110 percent of average); Pathfinder 994,600 acre feet (163 percent of average); Seminoe 753,000 acre feet (192 percent of average); and Wheatland No.2 77,000 acre feet (140 percent of average). Water allocated to project use is also above average with North Platte Project users at 136 percent of average, Kendrick Project users at 130 percent of average, and Glendo Project users at 134 percent of average.

Streamflow
Yields from 41 to 102 percent are expected in the 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 about 25,000 acre-feet (41 percent of average). Deer Creek at Glenrock is expected to yield about 46 percent of average (13,700 acre-feet). LaPrele Creek above the reservoir is estimated to yield 47 percent of average (9,400 acre-feet). North Platte River below Guernsey Reservoir is expected to yield about 73 percent of normal (597,000 acre-feet), and below Glendo Reservoir is anticipated to yield about 72 percent of average (573,000 acre-feet). Laramie River near Woods should yield about 102 percent of average (102,000 acre-feet). The Little Laramie near Filmore should produce about 42,000 acre-feet (69 percent of average).

 
==================================================================================================================================
                                      LOWER NORTH PLATTE, SWEETWATER & LARAMIE RIVER BASINS
                                               Streamflow Forecasts - May 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           MAY-JUL       9.0      13.7    |       23        41    |        32        46             56
                                     MAY-SEP       9.8      15.0    |       25        41    |        35        50             61
                                                                    |                       |
Deer Creek at Glenrock               MAY-SEP       8.4      11.4    |     13.7        46    |      16.2        20             30
                                                                    |                       |
La Prele Creek ab La Prele Reservoir MAY-SEP       2.4       5.8    |      9.4        47    |      14.3        24             20
                                                                    |                       |
North Platte River blw Glendo        MAY-SEP       431              |      573        72    |                 815            799
                                                                    |                       |
North Platte River blw Guernsey      MAY-SEP       453              |      597        73    |                 848            823
                                                                    |                       |
Laramie River nr Woods               MAY-SEP        84       111    |      129       102    |       147       174            127
                                                                    |                       |
Little Laramie River nr Filmore      MAY-SEP        33        38    |       42        69    |        46        52             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, 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    197.7    179.0    179.9 |   SWEETWATER                  3        53        73
                                                                        |
GLENDO                                 506.4    516.1    527.7    457.6 |   DEER & LaPRELE CREEKS       4        67        87
                                                                        |
GUERNSEY                                45.6     36.0     37.2     32.8 |   N PLATTE abv Laramie R.    27        73        80
                                                                        |
PATHFINDER                            1016.5    994.6    995.3    609.0 |   LARAMIE RIVER abv Laramie   9        82        82
                                                                        |
SEMINOE                               1016.7    753.0    719.8    392.0 |   LITTLE LARAMIE RIVER        4        48        49
                                                                        |
WHEATLAND #2                            98.9     77.0     76.0     54.9 |   LARAMIE RIVER above mouth  12        72        71
                                                                        |
NORTH PLATTE PROJ                     1062.1   1069.1   1061.8    786.7 |   NORTH PLATTE               35        71        77
                                                                        |
KENDRICK PROJECT                      1201.7   1047.4   1031.3    807.0 |
                                                                        |
GLENDO PROJECT USERS                   183.2    172.2    172.2    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 2000 Basin Outlook Report Contents Page

Lower North Platte River Basin (9) May 2000

Lower North Platte River Basin (9)
May 2000