January 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-1.2
2Tobacco River1.4
3Kootenai Ft. Steele to Libby Dam1.7
4Kootenai River below Libby Dam1.8
5Fisher River-0.5
6Yaak River0.7
7North Fk. Flathead River2.1
8Middle Fk. Flathead River1
9South Fk. Flathead River2.4
10Flathead River at Columbia Falls1.6
11Stillwater/Whitefish Rivers 
12Swan River0
13Flathead River at Polson1
14Mission Valley0.2
15Little Bitterroot River0.4
16Clark Fork River above Milltown-0.5
17Blackfoot River0
18Clark Fork River above Missoula0
19Bitterroot River0.4
20Clark Fork River below Bitterroot River0.1
21Clark Fork River below Flathead River0.7
22Beaverhead River-0.9
23Ruby River-0.4
24Big Hole River-1
25Boulder River (Jefferson)-0.4
26Jefferson River-0.2
27Madison River0.7
28Gallatin River-0.7
29Missouri River above Canyon Ferry-0.7
30Missouri River below Canyon Ferry-0.7
31Smith River-0.8
32Sun River-0.4
33Teton River0.8
34Birch/Dupuyer Creeks-2.4
35Marias River below Tiber Reservoir-0.5
36Musselshell River-1.7
37Missouri River above Fort Peck-1.1
38Missouri River below Fort Peck0
39Milk River 
40Dearborn River near Craig 
41Yellowstone River above Livingston2.8
42Shields River-1
43Boulder River (Yellowstone)-0.4
44Stillwater River0.4
45Rock/Red Lodge Creeks-0.7
46Clarks Fork River2.1
47Yellowstone River above Bighorn River2
48Bighorn River below Bighorn Lake2.1
49Little Bighorn River-1
50Yellowstone River below Bighorn River2
51Tongue River0.2
52Powder River-0.4
53Upper Judith Basin-2
54St. Mary River1.4