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

Lower North Platte River Basin (9)
April 2000

Snow
SWE for the North Platte River basin in Wyoming averages 88 percent of normal (103 % of last year). The Sweetwater drainage is currently 83 percent of average (82 % of last year). Deer and LaPrele Creeks are currently 90 percent of normal (119 percent of last year). SWE for the North Platte above the Laramie River drainage is 89 percent of average (103 % of last year). SWE for the Laramie River above the mouth is 86 percent of average (112 % of last year). SWE for the Laramie River above Laramie is 93 percent of average (116 % of last year). And SWE in the Little Laramie River is 73 percent of normal (103 % 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 40 to 156. March precipitation for the basin was 83 percent of average (174 percent of last year). The water year-to-date precipitation for the basin is currently 86 percent of average (77 percent of last year). Year to date percentages range from 54 to 107.

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 (97 percent of average); Glendo 463,600 acre feet (110 percent of average); Guernsey 18,600 acre feet (86 percent of average); Pathfinder 994,900 acre feet (161 percent of average); Seminoe 743,000 acre feet (202 percent of average); and Wheatland No.2 74,000 acre feet (152 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 62 to 81 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 46,000 acre-feet (62 percent of average). Deer Creek at Glenrock is expected to yield about 67 percent of average (26,000 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 80 percent of normal (771,000 acre-feet), and below Glendo Reservoir is anticipated to yield about 81 percent of average (803,000 acre-feet). Laramie River near Woods should yield about 77 percent of average (104,000 acre-feet). The Little Laramie near Filmore should produce about 40,000 acre-feet (63 percent of average).

 
==================================================================================================================================
                                      LOWER NORTH PLATTE, SWEETWATER & LARAMIE RIVER BASINS
                                               Streamflow Forecasts - April 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      17.3        27    |       43        62    |        59        83             69
                                     APR-SEP      18.5        30    |       46        62    |        63        87             74
                                                                    |                       |
Deer Creek at Glenrock               APR-SEP      12.9        20    |       26        67    |        33        44             39
                                                                    |                       |
La Prele Creek ab La Prele Reservoir APR-SEP       8.0      12.7    |       20        80    |        30        49             25
                                                                    |                       |
North Platte River blw Glendo        APR-SEP       453              |      771        80    |                1107            963
                                                                    |                       |
North Platte River blw Guernsey      APR-SEP       475              |      803        81    |                1147            989
                                                                    |                       |
Laramie River nr Woods               APR-SEP        41        78    |      104        77    |       130       167            135
                                                                    |                       |
Little Laramie River nr Filmore      APR-SEP        23        33    |       40        63    |        47        57             64
                                                                    |                       |
==================================================================================================================================
          LOWER NORTH PLATTE, SWEETWATER & LARAMIE RIVER BASINS         |  LOWER NORTH PLATTE, SWEETWATER & LARAMIE RIVER BASINS
             Reservoir Storage (1000 AF) - End of March                 |        Watershed Snowpack Analysis - April 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    162.3    162.0 |   SWEETWATER                  3        83        83
                                                                        |
GLENDO                                 506.4    463.6    505.5    420.3 |   DEER & LaPRELE CREEKS       2       129        87
                                                                        |
GUERNSEY                                45.6     18.6     29.9     21.6 |   N PLATTE abv Laramie R.    17       108        95
                                                                        |
PATHFINDER                            1016.5    994.9    973.5    619.0 |   LARAMIE RIVER abv Laramie   9       116        93
                                                                        |
SEMINOE                               1016.7    743.0    673.8    368.0 |   LITTLE LARAMIE RIVER        3        97        76
                                                                        |
WHEATLAND #2                            98.9     74.0     66.0     48.7 |   LARAMIE RIVER above mouth  11       111        89
                                                                        |
NORTH PLATTE PROJ                     1062.1   1065.2    999.0    676.0 |   NORTH PLATTE               25       109        93
                                                                        |
KENDRICK PROJECT                      1201.7    987.0    973.0    812.7 |
                                                                        |
GLENDO PROJECT USERS                   183.2    155.0    169.3    127.2 |
                                                                        |
==================================================================================================================================
 * 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.

To April 2000 Basin Outlook Report Contents Page

Lower North Platte River Basin (9) April 2000

Lower North Platte River Basin (9)
April 2000