Date: June 9, 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.

MAY STREAMFLOWS MOSTLY BELOW NORMAL
RESERVOIR STORAGE MOSTLY NORMAL

At eight long-term U.S. Geological Survey gaging stations, the monthly mean streamflows for the month of May were normal at three, above normal at four, and below normal at one.

Monthly mean streamflows were normal at:

Water storage remained normal at five out of six major hydroelectric reservoirs in Montana: Canyon Ferry Lake, Bighorn Lake, Lake Koocanusa, Flathead Lake, and Hungry Horse Reservoir. Storage was below normal in Fort Peck Lake.

For the month of May, water storage at all four major irrigation reservoirs was normal: Lima, Clark Canyon, Gibson, and Fresno Reservoirs.

Untitled Document
Station February monthly mean discharge, in ft3/s 1971-2000 Average discharge, in ft3/s Percent of average
Yaak River near Troy
2,600
3,320
78
Blackfoot River near Bonner
6,030
4,800
126
Clark Fork at St. Regis
23,410
19,800
118
Middle Fork Flathead River near West Glacier
8,090
9,250
87
Marias River near Shelby
2,300
2,400
96
Rock Creek below Horse Creek, near International Boundary
17.9
14.7
122
Yellowstone River at Corwin Springs
8,850
6,680
132
Yellowstone River at Billings
18,020
14,100
128

e, estimated.

Hydroelectric reservoirs

 February contents in acre-feet Percent of capacity Percent of 1971-2000 average
Canyon Ferry Lake
1,663,000
85
102
Fort Peck Lake
11,868,000
63
73
Bighorn Lake
891,700
66
103
Lake Koocanusa
3,924,000
68
120
Hungry Horse reservoir
2,908,000
84
112
Flathead Lake
1,480,000
84
100

Irrigation reservoirs
Lima Reservoir
69,760
85
106
Clark Canyon Reservoir
150,090
59
93
Gibson Reservoir
84,370
87
95
Fresno Reservoir
91,360
89
109