March 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 Reservoir0.4
2Tobacco River0.9
3Kootenai Ft. Steele to Libby Dam0.9
4Kootenai River below Libby Dam1.8
5Fisher River0
6Yaak River0.5
7North Fk. Flathead River1
8Middle Fk. Flathead River0.5
9South Fk. Flathead River3.1
10Flathead River at Columbia Falls1.6
11Stillwater/Whitefish Rivers 
12Swan River-0.4
13Flathead River at Polson0.9
14Mission Valley 
15Little Bitterroot River 
16Clark Fork River above Milltown0.7
17Blackfoot River0
18Clark Fork River above Missoula0
19Bitterroot River0.4
20Clark Fork River below Bitterroot River0.1
21Clark Fork River below Flathead River0.6
22Beaverhead River0.2
23Ruby River-0.7
24Big Hole River0.2
25Boulder River (Jefferson)-0.4
26Jefferson River0.6
27Madison River1
28Gallatin River-0.7
29Missouri River above Canyon Ferry0
30Missouri River below Canyon Ferry0
31Smith River0
32Sun River0.4
33Teton River1
34Birch/Dupuyer Creeks-1.9
35Marias River below Tiber Reservoir1.7
36Musselshell River-1.6
37Missouri River above Fort Peck0.4
38Missouri River below Fort Peck0.9
39Milk River 
40Dearborn River near Craig 
41Yellowstone River above Livingston3.1
42Shields River-0.6
43Boulder River (Yellowstone)0.4
44Stillwater River0.7
45Rock/Red Lodge Creeks-0.4
46Clarks Fork River3.3
47Yellowstone River above Bighorn River2.4
48Bighorn River below Bighorn Lake3.8
49Little Bighorn River-1
50Yellowstone River below Bighorn River3
51Tongue River0.4
52Powder River0.2
53Upper Judith Basin-0.4
54St. Mary River1.7