Date: January 11, 2009

Data in this release are preliminary. Final data will be provided in the annual report (WDR-US-2009), Water-resources data for the United States.

NOTES TO EDITOR: (1) ft3/s is an abbreviation for cubic feet per second which is the rate of discharge representing a volume of a cubic foot of water passing a given point during one second and is equivalent to 7.48 gallons per second or 448.8 gallons per minute. (2) the "normal" range is 80 to 120 percent of average.

DECEMBER STREAMFLOWS VARY
RESERVOIR STORAGE MOSTLY NORMAL

At eight long-term U.S. Geological Survey gaging stations, the monthly mean streamflow for the month of December was normal at one and below normal at seven. Monthly mean streamflow was normal at:

Contents of reservoirs at seven major hydroelectric reservoirs in Montana remained normal: Canyon Ferry Lake, Fort Peck Lake, Bighorn Lake, Lake Koocanusa, Hungry Horse Reservoir, and Flathead Lake.

For the month of December, contents at at two major irrigation reservoirs were normal: Lima and Clark Canyon Reservoirs. Contents were below normal in Gibson and Fresno Reservoirs.

Untitled Document
Station December monthly mean discharge, in ft3/s 1971-2000 Average discharge, in ft3/s Percent of average
Yaak River near Troy
105
345
30
Blackfoot River near Bonner
339
610
56
Clark Fork at St. Regis
2,280
3,410
67
Middle Fork Flathead River near West Glacier
515
941
55
Marias River near Shelby
188
334
56
Rock Creek below Horse Creek, near International Boundary
0.28
0.79
35
Yellowstone River at Corwin Springs
723
981
74
Yellowstone River at Billings
2,430
2,980
82

e, estimated.

Hydroelectric reservoirs

 December contents in acre-feet Percent of capacity Percent of 1971-2000 average
Canyon Ferry Lake
1,616,000
81
97
Fort Peck Lake
12,500,000
66
80
Bighorn Lake
971,000
72
107
Lake Koocanusa
3,746,000
65
119
Hungry Horse reservoir
2,894,000
84
120
Flathead Lake
1,209,000
68
101

Irrigation reservoirs
Lima Reservoir
39,140
47
117
Clark Canyon Reservoir
152,900
60
111
Gibson Reservoir
14,340
15
34
Fresno Reservoir
38,960
38
75