May 2014
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 NameValue
1Marias River above Tiber Reservoir1.8
1Marias River above Tiber Reservoir1.8
2Tobacco River1.6
2Tobacco River1.6
3Kootenai Ft. Steele to Libby Dam1
3Kootenai Ft. Steele to Libby Dam1
4Kootenai River below Libby Dam1.8
4Kootenai River below Libby Dam1.8
5Fisher River1.4
5Fisher River1.4
6Yaak River0.6
6Yaak River0.6
7North Fk. Flathead River1.4
7North Fk. Flathead River1.4
8Middle Fk. Flathead River1.9
8Middle Fk. Flathead River1.9
9South Fk. Flathead River2.1
9South Fk. Flathead River2.1
10Flathead River at Columbia Falls1.8
10Flathead River at Columbia Falls1.8
11Stillwater/Whitefish Rivers 
11Stillwater/Whitefish Rivers 
12Swan River2.9
12Swan River2.9
13Flathead River at Polson2.1
13Flathead River at Polson2.1
14Mission Valley-1.7
14Mission Valley-1.7
15Little Bitterroot River3.5
15Little Bitterroot River3.5
16Clark Fork River above Milltown2.3
16Clark Fork River above Milltown2.3
17Blackfoot River2.7
17Blackfoot River2.7
18Clark Fork River above Missoula2.7
18Clark Fork River above Missoula2.7
19Bitterroot River2.5
19Bitterroot River2.5
20Clark Fork River below Bitterroot River2.6
20Clark Fork River below Bitterroot River2.6
21Clark Fork River below Flathead River2.3
21Clark Fork River below Flathead River2.3
22Beaverhead River-1.9
22Beaverhead River-1.9
23Ruby River-0.5
23Ruby River-0.5
24Big Hole River1.4
24Big Hole River1.4
25Boulder River (Jefferson)2.1
25Boulder River (Jefferson)2.1
26Jefferson River1.9
26Jefferson River1.9
27Madison River1.6
27Madison River1.6
28Gallatin River2.1
28Gallatin River2.1
29Missouri River above Canyon Ferry1.9
29Missouri River above Canyon Ferry1.9
30Missouri River below Canyon Ferry0.8
30Missouri River below Canyon Ferry0.8
31Smith River2.4
31Smith River2.4
32Sun River1.2
32Sun River1.2
33Teton River1.9
33Teton River1.9
34Birch/Dupuyer Creeks-0.8
34Birch/Dupuyer Creeks-0.8
35Marias River below Tiber Reservoir2.7
35Marias River below Tiber Reservoir2.7
36Musselshell River2.6
36Musselshell River2.6
37Missouri River above Fort Peck0.4
37Missouri River above Fort Peck0.4
38Missouri River below Fort Peck-0.1
38Missouri River below Fort Peck-0.1
39Milk River0.8
39Milk River0.8
40Dearborn River near Craig2.6
40Dearborn River near Craig2.6
41Yellowstone River above Livingston3.1
41Yellowstone River above Livingston3.1
42Shields River2.6
42Shields River2.6
43Boulder River (Yellowstone)2.7
43Boulder River (Yellowstone)2.7
44Stillwater River2.7
44Stillwater River2.7
45Rock/Red Lodge Creeks2.9
45Rock/Red Lodge Creeks2.9
46Clarks Fork River3.4
46Clarks Fork River3.4
47Yellowstone River above Bighorn River3
47Yellowstone River above Bighorn River3
48Bighorn River below Bighorn Lake1.9
48Bighorn River below Bighorn Lake1.9
49Little Bighorn River2.5
49Little Bighorn River2.5
50Yellowstone River below Bighorn River2.5
50Yellowstone River below Bighorn River2.5
51Tongue River2.7
51Tongue River2.7
52Powder River2.7
52Powder River2.7
53Upper Judith Basin1.1
53Upper Judith Basin1.1
54St. Mary River1.8
54St. Mary River1.8