September 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 Reservoir-1.22
2Tobacco River-1.04
3Kootenai Ft. Steele to Libby Dam-1.56
4Kootenai River below Libby Dam-0.91
5Fisher River-1.74
6Yaak River-1.25
7North Fk. Flathead River-0.69
8Middle Fk. Flathead River-1.39
9South Fk. Flathead River-0.69
10Flathead River at Columbia Falls-0.52
12Swan River-0.87
13Flathead River at Polson-1.56
14Mission Valley 
15Little Bitterroot River-1
16Clark Fork River above Milltown0.17
17Blackfoot River-0.69
18Clark Fork River above Missoula-0.52
19Bitterroot River-0.52
20Clark Fork River below Bitterroot River-0.52
21Clark Fork River below Flathead River-1.1856
22Beaverhead River0.17
23Ruby River-0.69
24Big Hole River0.35
25Boulder River (Jefferson)-1.22
26Jefferson River0.21
27Madison River0
28Gallatin River-1.56
29Missouri River above Canyon Ferry-0.17
30Missouri River below Canyon Ferry-0.87
31Smith River-2.27
32Sun River-1.74
33Teton River-0.76
34Birch/Dupuyer Creeks-1.39
35Marias River below Tiber Reservoir0.52
36Musselshell River-1.74
37Missouri River above Fort Peck-0.6285
38Missouri River below Fort Peck-0.17
39Milk River-1.74
40Dearborn River near Craig-0.83
41Yellowstone River above Livingston2.43
42Shields River-1.04
43Boulder River (Yellowstone)0.17
44Stillwater River1.04
45Rock/Red Lodge Creeks0.87
46Clarks Fork River1.74
47Yellowstone River above Bighorn River1.7322
48Bighorn River below Bighorn Lake2.12271
49Little Bighorn River0
50Yellowstone River below Bighorn River2.12271
51Tongue River1.56
52Powder River-0.87
53Upper Judith Basin-3.7
54St. Mary River-1.22