June 2017
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 Reservoir1.22
2Tobacco River0
3Kootenai Ft. Steele to Libby Dam0.87
4Kootenai River below Libby Dam0.18
5Fisher River1.04
6Yaak River0.52
7North Fk. Flathead River1.39
8Middle Fk. Flathead River1.04
9South Fk. Flathead River3.13
10Flathead River at Columbia Falls1.74
12Swan River1.74
13Flathead River at Polson1.22
14Mission Valley2.31
15Little Bitterroot River1.1
16Clark Fork River above Milltown0.87
17Blackfoot River1.04
18Clark Fork River above Missoula1.04
19Bitterroot River-0.17
20Clark Fork River below Bitterroot River0.677
21Clark Fork River below Flathead River1.02452
22Beaverhead River0.52
23Ruby River0.52
24Big Hole River0.69
25Boulder River (Jefferson)-0.17
26Jefferson River1.04
27Madison River1.22
28Gallatin River0
29Missouri River above Canyon Ferry0.17
30Missouri River below Canyon Ferry0.52
31Smith River0
32Sun River1.22
33Teton River0.95
34Birch/Dupuyer Creeks0.52
35Marias River below Tiber Reservoir2.6
36Musselshell River0.69
37Missouri River above Fort Peck1.2556
38Missouri River below Fort Peck1.22
39Milk River 
40Dearborn River near Craig 
41Yellowstone River above Livingston2.08
42Shields River1.46
43Boulder River (Yellowstone)0.87
44Stillwater River1.39
45Rock/Red Lodge Creeks1.74
46Clarks Fork River2.6
47Yellowstone River above Bighorn River1.8278
48Bighorn River below Bighorn Lake3.8
49Little Bighorn River1
50Yellowstone River below Bighorn River2.72429
51Tongue River2.43
52Powder River2.78
53Upper Judith Basin 
54St. Mary River1.74
999Kootenai at Ft. Steele (Kootenay in Canada)