March 2015
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 NameValue
1Marias River above Tiber Reservoir-0.7
1Marias River above Tiber Reservoir-0.7
2Tobacco River-1.4
2Tobacco River-1.4
3Kootenai Ft. Steele to Libby Dam-1.4
3Kootenai Ft. Steele to Libby Dam-1.4
4Kootenai River below Libby Dam1.3
4Kootenai River below Libby Dam1.3
5Fisher River-2.4
5Fisher River-2.4
6Yaak River-2.4
6Yaak River-2.4
7North Fk. Flathead River-1.8
7North Fk. Flathead River-1.8
8Middle Fk. Flathead River-0.7
8Middle Fk. Flathead River-0.7
9South Fk. Flathead River2.9
9South Fk. Flathead River2.9
10Flathead River at Columbia Falls0.7
10Flathead River at Columbia Falls0.7
11Stillwater/Whitefish Rivers 
11Stillwater/Whitefish Rivers 
12Swan River0.7
12Swan River0.7
13Flathead River at Polson0.2
13Flathead River at Polson0.2
14Mission Valley0.2
14Mission Valley0.2
15Little Bitterroot River-0.2
15Little Bitterroot River-0.2
16Clark Fork River above Milltown0.7
16Clark Fork River above Milltown0.7
17Blackfoot River-0.2
17Blackfoot River-0.2
18Clark Fork River above Missoula0.2
18Clark Fork River above Missoula0.2
19Bitterroot River-0.2
19Bitterroot River-0.2
20Clark Fork River below Bitterroot River0.1
20Clark Fork River below Bitterroot River0.1
21Clark Fork River below Flathead River0.1
21Clark Fork River below Flathead River0.1
22Beaverhead River-1.8
22Beaverhead River-1.8
23Ruby River-1.8
23Ruby River-1.8
24Big Hole River0.5
24Big Hole River0.5
25Boulder River (Jefferson)0.2
25Boulder River (Jefferson)0.2
26Jefferson River-0.4
26Jefferson River-0.4
27Madison River-1.8
27Madison River-1.8
28Gallatin River-0.9
28Gallatin River-0.9
29Missouri River above Canyon Ferry-0.9
29Missouri River above Canyon Ferry-0.9
30Missouri River below Canyon Ferry-0.9
30Missouri River below Canyon Ferry-0.9
31Smith River2.1
31Smith River2.1
32Sun River-1.1
32Sun River-1.1
33Teton River0.6
33Teton River0.6
34Birch/Dupuyer Creeks-0.5
34Birch/Dupuyer Creeks-0.5
35Marias River below Tiber Reservoir2
35Marias River below Tiber Reservoir2
36Musselshell River0.9
36Musselshell River0.9
37Missouri River above Fort Peck0.5
37Missouri River above Fort Peck0.5
38Missouri River below Fort Peck0.4
38Missouri River below Fort Peck0.4
39Milk River 
39Milk River 
40Dearborn River near Craig-0.5
40Dearborn River near Craig-0.5
41Yellowstone River above Livingston0.2
41Yellowstone River above Livingston0.2
42Shields River-0.7
42Shields River-0.7
43Boulder River (Yellowstone)0.2
43Boulder River (Yellowstone)0.2
44Stillwater River0.2
44Stillwater River0.2
45Rock/Red Lodge Creeks0.7
45Rock/Red Lodge Creeks0.7
46Clarks Fork River1.6
46Clarks Fork River1.6
47Yellowstone River above Bighorn River0.4
47Yellowstone River above Bighorn River0.4
48Bighorn River below Bighorn Lake0.5
48Bighorn River below Bighorn Lake0.5
49Little Bighorn River0
49Little Bighorn River0
50Yellowstone River below Bighorn River0.5
50Yellowstone River below Bighorn River0.5
51Tongue River0.5
51Tongue River0.5
52Powder River0.2
52Powder River0.2
53Upper Judith Basin3.7
53Upper Judith Basin3.7
54St. Mary River-2.7
54St. Mary River-2.7