March 2016
Surface Water Supply Index Report

Provided by the US Natural Resources Conservation Service
Bozeman, Montana

The SWSI is designed for areas that rely primarily on snowmelt runoff as the primary source of surface water. The SWSI accounts for snowpack, mountain precipitation, streamflow, reservoir contents, and soil moisture conditions. The SWSI can be used by irrigators, fisheries personnel, recreationists, and others who utilize surface waters. SWSI values are categorized as follows:

IDBasin NameSWSI
1Marias River above Tiber Reservoir-2.6
1Marias River above Tiber Reservoir-2.6
2Tobacco River-0.6
2Tobacco River-0.6
3Kootenai Ft. Steele to Libby Dam-0.3
3Kootenai Ft. Steele to Libby Dam-0.3
4Kootenai River below Libby Dam1.8
4Kootenai River below Libby Dam1.8
5Fisher River-0.8
5Fisher River-0.8
6Yaak River0.4
6Yaak River0.4
7North Fk. Flathead River-1.2
7North Fk. Flathead River-1.2
8Middle Fk. Flathead River-1.5
8Middle Fk. Flathead River-1.5
9South Fk. Flathead River-0.1
9South Fk. Flathead River-0.1
10Flathead River at Columbia Falls-0.6
10Flathead River at Columbia Falls-0.6
11Stillwater/Whitefish Rivers 
11Stillwater/Whitefish Rivers 
12Swan River0.1
12Swan River0.1
13Flathead River at Polson-1.2
13Flathead River at Polson-1.2
14Mission Valley-2.5
14Mission Valley-2.5
15Little Bitterroot River-2
15Little Bitterroot River-2
16Clark Fork River above Milltown-0.1
16Clark Fork River above Milltown-0.1
17Blackfoot River-1.5
17Blackfoot River-1.5
18Clark Fork River above Missoula-1
18Clark Fork River above Missoula-1
19Bitterroot River-0.9
19Bitterroot River-0.9
20Clark Fork River below Bitterroot River-0.7
20Clark Fork River below Bitterroot River-0.7
21Clark Fork River below Flathead River-1
21Clark Fork River below Flathead River-1
22Beaverhead River-1.2
22Beaverhead River-1.2
23Ruby River-0.4
23Ruby River-0.4
24Big Hole River0.6
24Big Hole River0.6
25Boulder River (Jefferson)0.3
25Boulder River (Jefferson)0.3
26Jefferson River0.1
26Jefferson River0.1
27Madison River-1.3
27Madison River-1.3
28Gallatin River-1
28Gallatin River-1
29Missouri River above Canyon Ferry-0.8
29Missouri River above Canyon Ferry-0.8
30Missouri River below Canyon Ferry-0.4
30Missouri River below Canyon Ferry-0.4
31Smith River0.2
31Smith River0.2
32Sun River-3.6
32Sun River-3.6
33Teton River-2.2
33Teton River-2.2
34Birch/Dupuyer Creeks-2.8
34Birch/Dupuyer Creeks-2.8
35Marias River below Tiber Reservoir-2.6
35Marias River below Tiber Reservoir-2.6
36Musselshell River-0.1
36Musselshell River-0.1
37Missouri River above Fort Peck-0.7
37Missouri River above Fort Peck-0.7
38Missouri River below Fort Peck0.1
38Missouri River below Fort Peck0.1
39Milk River 
39Milk River 
40Dearborn River near Craig-2.1
40Dearborn River near Craig-2.1
41Yellowstone River above Livingston-0.6
41Yellowstone River above Livingston-0.6
42Shields River-1
42Shields River-1
43Boulder River (Yellowstone)-1.9
43Boulder River (Yellowstone)-1.9
44Stillwater River-1.9
44Stillwater River-1.9
45Rock/Red Lodge Creeks-1.3
45Rock/Red Lodge Creeks-1.3
46Clarks Fork River-1.2
46Clarks Fork River-1.2
47Yellowstone River above Bighorn River-0.8
47Yellowstone River above Bighorn River-0.8
48Bighorn River below Bighorn Lake-0.8
48Bighorn River below Bighorn Lake-0.8
49Little Bighorn River-3.3
49Little Bighorn River-3.3
50Yellowstone River below Bighorn River-0.8
50Yellowstone River below Bighorn River-0.8
51Tongue River-3.1
51Tongue River-3.1
52Powder River-2.8
52Powder River-2.8
53Upper Judith Basin1
53Upper Judith Basin1
54St. Mary River-1.2
54St. Mary River-1.2