Date: August 4, 2008

Data in this release are preliminary. Final data will be provided in the annual report (WDR-US-2007), 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.

JULY STREAMFLOWS MOSTLY ABOVE NORMAL
RESERVOIR STORAGE MOSTLY NORMAL

At eight long-term U.S. Geological Survey gaging stations, the monthly mean streamflows for the month of July were above normal at five, normal at one, and below normal at two. The flow on the Clark Fork at St. Regis, Middle Fork Flathead River near West Glacier, Marias River near Shelby, Yellowstone River at Corwin Springs, and Yellowstone River at Billings was above normal. Flow on the Blackfoot River near Bonner was in the normal range. The Yaak River near Troy and Rock Creek below Horse Creek, near the international boundary had flow below normal.

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

For the month of July, water storage at four major irrigation reservoirs was above normal at one, normal at two, and below normal at one. Storage at Fresno Reservoir was above normal, Lima and Gibson Reservoirs was normal, and Clark Canyon Reservoir remained below normal.

The following summary lists preliminary streamflow and reservoir data and long-term-average values for purposes of comparison.

Untitled Document
Station July monthly mean discharge, in ft3/s 1971-2000 Average discharge, in ft3/s Percent of average
Yaak River near Troy
375
523
72
Blackfoot River near Bonner
2,060
1,740
118
Clark Fork at St. Regis
11,060
7,950
139
Middle Fork Flathead River nr West Glacier
5,620
4,010
140
Marias River near Shelby
1,100
882
125
Rock Creek below Horse Creek, nr Int'l Bndry
0.10
10.8
1
Yellowstone River at Corwin Springs
10,620
6,960
153
Yellowstone River at Billings
23,300
14,700
152

Hydroelectric reservoirs

 July contents in acre-feet Percent of capacity Percent of 1971-2000 average
Canyon Ferry Lake
1,899,000
95
104
Fort Peck Lake
10,580,000
56
63
Bighorn Lake
1,074,000
79
106
Lake Koocanusa
5,073,000
88
95
Hungry Horse reservoir
3,293,000
95
103
Flathead Lake
1,754,000
98
99

Irrigation reservoirs
Lima Reservoir
43,320
52
95
Clark Canyon Reservoir
78,160
31
57
Gibson Reservoir
64,660
67
109
Fresno Reservoir
74,580
72
122