August 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-0.5
2Tobacco River-0.3
3Kootenai Ft. Steele to Libby Dam0.9
4Kootenai River below Libby Dam0.4
5Fisher River-1
6Yaak River0
7North Fk. Flathead River0.9
8Middle Fk. Flathead River0.5
9South Fk. Flathead River0.5
10Flathead River at Columbia Falls0.4
12Swan River0.9
13Flathead River at Polson0.7
14Mission Valley 
15Little Bitterroot River 
16Clark Fork River above Milltown1
17Blackfoot River0.5
18Clark Fork River above Missoula0.7
19Bitterroot River1.4
20Clark Fork River below Bitterroot River0.9
21Clark Fork River below Flathead River0.8
22Beaverhead River0.5
23Ruby River-0.9
24Big Hole River1.7
25Boulder River (Jefferson)0
26Jefferson River1
27Madison River0.9
28Gallatin River-0.9
29Missouri River above Canyon Ferry0.4
30Missouri River below Canyon Ferry0
31Smith River-2.3
32Sun River-0.4
33Teton River-0.4
34Birch/Dupuyer Creeks0
35Marias River below Tiber Reservoir0.2
36Musselshell River-0.5
37Missouri River above Fort Peck-0.7
38Missouri River below Fort Peck 
39Milk River 
40Dearborn River near Craig 
41Yellowstone River above Livingston2.4
42Shields River0.4
43Boulder River (Yellowstone)1.4
44Stillwater River2.6
45Rock/Red Lodge Creeks0.9
46Clarks Fork River2.8
47Yellowstone River above Bighorn River2.3
48Bighorn River below Bighorn Lake3.8
49Little Bighorn River-1.2
50Yellowstone River below Bighorn River3
51Tongue River1.4
52Powder River1
53Upper Judith Basin-3.5
54St. Mary River0.2