Date: May 1, 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.

REPORT OF APRIL STREAMFLOWS
AND RESERVOIR STORAGE

The monthly mean streamflows at eight long-term U.S. Geological Survey gaging stations remained below normal for April:

Storage at three out of six major hydroelectric reservoirs in Montana was in the normal range, one was above normal, and two were below normal. Storage for April was normal at Canyon Ferry Lake, Bighorn Lake, and Hungry Horse Reservoir. Storage was above normal in Lake Koocanusa and below normal in Fort Peck and Flathead Lakes.

For the month of April, water storage remained below normal at four major irrigation reservoirs: Lima, Clark Canyon, Gibson, and Fresno Reservoirs.

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

Untitled Document
Station March monthly mean discharge, in ft3/s 1971-2000 Average discharge, in ft3/s Percent of average
Yaak River near Troy
581
1,960
30
Blackfoot River near Bonner
876
2,140
41
Clark Fork at St. Regis
4,410
9,000
4.9
Middle Fork Flathead River nr West Glacier
1,120
3,300
34
Marias River near Shelby
330
1,000
33
Rock Creek below Horse Creek, nr Int'l Bndry
5.75
75
7.6
Yellowstone River at Corwin Springs
1,160
1,730
67
Yellowstone River at Billings
2,400
4,440
54

Hydroelectric reservoirs

 March contents in acre-feet Percent of capacity Percent of 1971-2000 average
Canyon Ferry Lake
1,432,000
72
97
Fort Peck Lake
8,811,000
47
57
Bighorn Lake
779,600
57
98
Lake Koocanusa
3,227,000
56
137
Hungry Horse reservoir
2,184,000
63
112
Flathead Lake
671,800
38
72

Irrigation reservoirs
Lima Reservoir
30,350
36
53
Clark Canyon Reservoir
122,700
48
76
Gibson Reservoir
22,740
24
37
Fresno Reservoir
43,250
42
48