Hydrology: Explore the Jocko Watershed

In addition to streams and how they function, hydrologists consider a number of other factors when they study a watershed including vegetation, precipitation, roads, land ownership, and protected areas.

    Base Map
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    The Jocko Watershed

    The Jocko River drainage basin is the second largest tributary watershed of the lower Flathead River in the Clark Fork River Basin. At its mouth, the Jocko has an annual average discharge of 238 cubic feet per second. The Jocko River drains a watershed area of 246,263 acres, with approximately 5% of the drainage under irrigation. The watershed includes the South Fork of the Jocko Primitive Area, the Pistol Creek Mountains, the Ninemile Divide area from Evaro to Valley Creek, and the communities of Arlee, Ravalli, and Evaro. Three headwater tributaries — the North, Middle, and South Forks — join to form the Jocko River. Below the confluence of the three forks, the river flows west to the town of Arlee. Above Arlee, it cuts through a confined valley and is high gradient, typical of mountain streams. Below Arlee, the Jocko flows north through the Jocko Valley and becomes less confined, flowing through a broad valley of forest, wetlands, and agricultural land. Finley and Valley Creeks flow into the Jocko below Arlee.

    Tributaries
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    The Tributaries

    • Finley CreekSize (acres): 50,752 Size (sq miles): 79.3 Ave. Annual Precip. (inches): 26 Flow (2-yr Return Interval Flood): 329 Flow (50-yr Return Interval Flood): 965
    • Valley CreekSize (acres): 41,835 Size (sq miles): 65.4 Ave Annual Precip. (inches): 25 Flow (2-yr Return Interval Flood): 259 Flow (50-yr Return Interval Flood): 780
    • Spring CreekSize (acres): 14,888 Size (sq miles): 23.3 Ave Annual Precip. (inches): 18 Flow (2-yr Return Interval Flood): 45 Flow (50-yr Return Interval Flood): 150
    • Pistol CreekSize (acres): 7,407 Size (sq miles): 11.6 Ave Annual Precip. (inches): 29 Flow (2-yr Return Interval Flood): 63 Flow (50-yr Return Interval Flood): 209
    • North Fork of the Jocko RiverSize (acres): 25,216 Size (sq miles): 39.4 Ave Annual Precip. (inches): 52 Flow (2-yr Return Interval Flood): 478 Flow (50-yr Return Interval Flood): 1189
    • Middle Fork of the Jocko RiverSize (acres): 9,920 Size (sq miles): 15.5 Ave Annual Precip. (inches): 38 Flow (2-yr Return Interval Flood): 125 Flow (50-yr Return Interval Flood): 369
    • South Fork of the Jocko RiverSize (acres): 37,376 Size (sq miles): 58.4 Ave Annual Precip. (inches): 39 Flow (2-yr Return Interval Flood): 451 Flow (50-yr Return Interval Flood): 1192
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    Canals
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    Canals

    Canals and the irrigation system they serve have perhaps the most important influence on the hydrology of the Jocko. In all but the wettest years, irrigation withdrawals reduce peak flows in much of the drainage. The reduction affects everything from fish to the riparian zone.

    Vegetation
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    Vegetation

    • Forested acresApproximate Percentage of Watershed: 73% Available for Harvest (acres): 79,100 Harvest Allowed but Restricted (acres): 37100 Unavailable for Harvest (acres): 8,800
    • Grassland acresApproximate Percentage of Watershed: 19%. Native grasslands are primarily the Palouse Prairie bunchgrass type and includes various wheatgrasses, fescues, blue grasses, needle-grasses, forbs, and sedges.
    • Cropland acresApproximate Percentage of Watershed: 6.5%. Percentage that is forage crops (primarily alfalfa) and tame grass mixtures (timothy, orchard grass, & brome grass): 70 to 80%. Percentage in small grains (wheat, barley, & oats): 20 to 30%
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    Precipitation
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    Precipitation

    Precipitation is the source of the water in the Jocko River. Knoweldge of the timing, location, and amount of precipitation is key to the development of accur-ate hydrologic models of the Jocko River.

    Roads
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    Roads

    Too many roads and/or poorly designed roads can lead to increases in sediment in a stream, altered streamflows, and less stable stream channels.

    • High to Very HighRoad densities from 2.1 to 4 miles of road per square mile are considered high. Road densities greater than 4.1 mies of road per square mile are considered very high. Biologists consider high road densities a threat to healthy fish and wildlife populations.
    • ModerateRoad densities from 1.1 to 1 mile of road per square mile are considered moderate.
    • RoadlessRoadless lands are primarily found in the Mission Mountains Tribal Wilderness and the South Fork of the Jocko Primitive Area.
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    Land Ownership
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    Land Ownership

    Land ownership often determines land use, and land use can affect the stability of a stream channel, the quality and quantity of the water entering the stream and condition of vegetation in the watershed.

    Protected Areas
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    Protected Areas

    Protected areas like wilderness and primitive areas are managed to maintain natural processes and to protect key attributes like water quality, riparian and aquatic habitats, and natural stream flows. They also serve as refuges for many vulnerable fish and wildlife species.

    • South Fork of the Jocko Primitive AreaIn 1974, the Tribal Council set aside the South Fork of the Jocko Primitive Area as a recreational and cultural use area. In 1979 they restricted use of the area to Tribal members and their families, and in 1990, they expanded the area to include several drainages. Logging is no longer permitted in the area, although motorized vehicles are allowed on designated roads.
    • Mission Mountains Tribal Wilderness AreaEstablished in 1982, the Mission Mountains Tribal Wilderness encompasses 91,778 acres. About 20,500 acres of the wilderness lie within the Jocko Drainage. Motorized vehicles are not allowed in the wilderness and the area is managed to maintain its pristine character.
    • Show More

Hydrology: Explore the Jocko Watershed

In addition to streams and how they function, hydrologists consider a number of other factors when they study a watershed including vegetation, precipitation, roads, land ownership, and protected areas.

    Base Map
    My Image

    The Jocko Watershed

    The Jocko River drainage basin is the second largest tributary watershed of the lower Flathead River in the Clark Fork River Basin. At its mouth, the Jocko has an annual average discharge of 238 cubic feet per second. The Jocko River drains a watershed area of 246,263 acres, with approximately 5% of the drainage under irrigation. The watershed includes the South Fork of the Jocko Primitive Area, the Pistol Creek Mountains, the Ninemile Divide area from Evaro to Valley Creek, and the communities of Arlee, Ravalli, and Evaro. Three headwater tributaries — the North, Middle, and South Forks — join to form the Jocko River. Below the confluence of the three forks, the river flows west to the town of Arlee. Above Arlee, it cuts through a confined valley and is high gradient, typical of mountain streams. Below Arlee, the Jocko flows north through the Jocko Valley and becomes less confined, flowing through a broad valley of forest, wetlands, and agricultural land. Finley and Valley Creeks flow into the Jocko below Arlee.

    Tributaries
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    The Tributaries

    • Finley CreekSize (acres): 50,752 Size (sq miles): 79.3 Ave. Annual Precip. (inches): 26 Flow (2-yr Return Interval Flood): 329 Flow (50-yr Return Interval Flood): 965
    • Valley CreekSize (acres): 41,835 Size (sq miles): 65.4 Ave Annual Precip. (inches): 25 Flow (2-yr Return Interval Flood): 259 Flow (50-yr Return Interval Flood): 780
    • Spring CreekSize (acres): 14,888 Size (sq miles): 23.3 Ave Annual Precip. (inches): 18 Flow (2-yr Return Interval Flood): 45 Flow (50-yr Return Interval Flood): 150
    • Pistol CreekSize (acres): 7,407 Size (sq miles): 11.6 Ave Annual Precip. (inches): 29 Flow (2-yr Return Interval Flood): 63 Flow (50-yr Return Interval Flood): 209
    • North Fork of the Jocko RiverSize (acres): 25,216 Size (sq miles): 39.4 Ave Annual Precip. (inches): 52 Flow (2-yr Return Interval Flood): 478 Flow (50-yr Return Interval Flood): 1189
    • Middle Fork of the Jocko RiverSize (acres): 9,920 Size (sq miles): 15.5 Ave Annual Precip. (inches): 38 Flow (2-yr Return Interval Flood): 125 Flow (50-yr Return Interval Flood): 369
    • South Fork of the Jocko RiverSize (acres): 37,376 Size (sq miles): 58.4 Ave Annual Precip. (inches): 39 Flow (2-yr Return Interval Flood): 451 Flow (50-yr Return Interval Flood): 1192
    • Show More
    Canals
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    Canals

    Canals and the irrigation system they serve have perhaps the most important influence on the hydrology of the Jocko. In all but the wettest years, irrigation withdrawals reduce peak flows in much of the drainage. The reduction affects everything from fish to the riparian zone.

    Vegetation
    My Image

    Vegetation

    • Forested acresApproximate Percentage of Watershed: 73% Available for Harvest (acres): 79,100 Harvest Allowed but Restricted (acres): 37100 Unavailable for Harvest (acres): 8,800
    • Grassland acresApproximate Percentage of Watershed: 19%. Native grasslands are primarily the Palouse Prairie bunchgrass type and includes various wheatgrasses, fescues, blue grasses, needle-grasses, forbs, and sedges.
    • Cropland acresApproximate Percentage of Watershed: 6.5%. Percentage that is forage crops (primarily alfalfa) and tame grass mixtures (timothy, orchard grass, & brome grass): 70 to 80%. Percentage in small grains (wheat, barley, & oats): 20 to 30%
    • Show More
    Precipitation
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    Precipitation

    Precipitation is the source of the water in the Jocko River. Knoweldge of the timing, location, and amount of precipitation is key to the development of accur-ate hydrologic models of the Jocko River.

    Roads
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    Roads

    Too many roads and/or poorly designed roads can lead to increases in sediment in a stream, altered streamflows, and less stable stream channels.

    • High to Very HighRoad densities from 2.1 to 4 miles of road per square mile are considered high. Road densities greater than 4.1 mies of road per square mile are considered very high. Biologists consider high road densities a threat to healthy fish and wildlife populations.
    • ModerateRoad densities from 1.1 to 1 mile of road per square mile are considered moderate.
    • RoadlessRoadless lands are primarily found in the Mission Mountains Tribal Wilderness and the South Fork of the Jocko Primitive Area.
    • Show More
    Land Ownership
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    Land Ownership

    Land ownership often determines land use, and land use can affect the stability of a stream channel, the quality and quantity of the water entering the stream and condition of vegetation in the watershed.

    Protected Areas
    My Image

    Protected Areas

    Protected areas like wilderness and primitive areas are managed to maintain natural processes and to protect key attributes like water quality, riparian and aquatic habitats, and natural stream flows. They also serve as refuges for many vulnerable fish and wildlife species.

    • South Fork of the Jocko Primitive AreaIn 1974, the Tribal Council set aside the South Fork of the Jocko Primitive Area as a recreational and cultural use area. In 1979 they restricted use of the area to Tribal members and their families, and in 1990, they expanded the area to include several drainages. Logging is no longer permitted in the area, although motorized vehicles are allowed on designated roads.
    • Mission Mountains Tribal Wilderness AreaEstablished in 1982, the Mission Mountains Tribal Wilderness encompasses 91,778 acres. About 20,500 acres of the wilderness lie within the Jocko Drainage. Motorized vehicles are not allowed in the wilderness and the area is managed to maintain its pristine character.
    • Show More

Hydrology: Explore the Jocko Watershed

In addition to streams and how they function, hydrologists consider a number of other factors when they study a watershed including vegetation, precipitation, roads, land ownership, and protected areas. Click on a tab and then scroll down to see the map.

    Base Map
    My Image

    The Jocko Watershed

    The Jocko River drainage basin is the second largest tributary watershed of the lower Flathead River in the Clark Fork River Basin. At its mouth, the Jocko has an annual average discharge of 238 cubic feet per second. The Jocko River drains a watershed area of 246,263 acres, with approximately 5% of the drainage under irrigation. The watershed includes the South Fork of the Jocko Primitive Area, the Pistol Creek Mountains, the Ninemile Divide area from Evaro to Valley Creek, and the communities of Arlee, Ravalli, and Evaro. Three headwater tributaries — the North, Middle, and South Forks — join to form the Jocko River. Below the confluence of the three forks, the river flows west to the town of Arlee. Above Arlee, it cuts through a confined valley and is high gradient, typical of mountain streams. Below Arlee, the Jocko flows north through the Jocko Valley and becomes less confined, flowing through a broad valley of forest, wetlands, and agricultural land. Finley and Valley Creeks flow into the Jocko below Arlee.

    Tributaries
    My Image

    The Tributaries

    • Finley CreekSize (acres): 50,752 Size (sq miles): 79.3 Ave. Annual Precip. (inches): 26 Flow (2-yr Return Interval Flood): 329 Flow (50-yr Return Interval Flood): 965
    • Valley CreekSize (acres): 41,835 Size (sq miles): 65.4 Ave Annual Precip. (inches): 25 Flow (2-yr Return Interval Flood): 259 Flow (50-yr Return Interval Flood): 780
    • Spring CreekSize (acres): 14,888 Size (sq miles): 23.3 Ave Annual Precip. (inches): 18 Flow (2-yr Return Interval Flood): 45 Flow (50-yr Return Interval Flood): 150
    • Pistol CreekSize (acres): 7,407 Size (sq miles): 11.6 Ave Annual Precip. (inches): 29 Flow (2-yr Return Interval Flood): 63 Flow (50-yr Return Interval Flood): 209
    • North Fork of the Jocko RiverSize (acres): 25,216 Size (sq miles): 39.4 Ave Annual Precip. (inches): 52 Flow (2-yr Return Interval Flood): 478 Flow (50-yr Return Interval Flood): 1189
    • Middle Fork of the Jocko RiverSize (acres): 9,920 Size (sq miles): 15.5 Ave Annual Precip. (inches): 38 Flow (2-yr Return Interval Flood): 125 Flow (50-yr Return Interval Flood): 369
    • South Fork of the Jocko RiverSize (acres): 37,376 Size (sq miles): 58.4 Ave Annual Precip. (inches): 39 Flow (2-yr Return Interval Flood): 451 Flow (50-yr Return Interval Flood): 1192
    • Show More
    Canals
    My Image

    Canals

    Canals and the irrigation system they serve have perhaps the most important influence on the hydrology of the Jocko. In all but the wettest years, irrigation withdrawals reduce peak flows in much of the drainage. The reduction affects everything from fish to the riparian zone.

    Vegetation
    My Image

    Vegetation

    • Forested acresApproximate Percentage of Watershed: 73% Available for Harvest (acres): 79,100 Harvest Allowed but Restricted (acres): 37100 Unavailable for Harvest (acres): 8,800
    • Grassland acresApproximate Percentage of Watershed: 19%. Native grasslands are primarily the Palouse Prairie bunchgrass type and includes various wheatgrasses, fescues, blue grasses, needle-grasses, forbs, and sedges.
    • Cropland acresApproximate Percentage of Watershed: 6.5%. Percentage that is forage crops (primarily alfalfa) and tame grass mixtures (timothy, orchard grass, & brome grass): 70 to 80%. Percentage in small grains (wheat, barley, & oats): 20 to 30%
    • Show More
    Precipitation
    My Image

    Precipitation

    Precipitation is the source of the water in the Jocko River. Knoweldge of the timing, location, and amount of precipitation is key to the development of accur-ate hydrologic models of the Jocko River.

    Roads
    My Image

    Roads

    Too many roads and/or poorly designed roads can lead to increases in sediment in a stream, altered streamflows, and less stable stream channels.

    • High to Very HighRoad densities from 2.1 to 4 miles of road per square mile are considered high. Road densities greater than 4.1 mies of road per square mile are considered very high. Biologists consider high road densities a threat to healthy fish and wildlife populations.
    • ModerateRoad densities from 1.1 to 1 mile of road per square mile are considered moderate.
    • RoadlessRoadless lands are primarily found in the Mission Mountains Tribal Wilderness and the South Fork of the Jocko Primitive Area.
    • Show More
    Land Ownership
    My Image

    Land Ownership

    Land ownership often determines land use, and land use can affect the stability of a stream channel, the quality and quantity of the water entering the stream and condition of vegetation in the watershed.

    Protected Areas
    My Image

    Protected Areas

    Protected areas like wilderness and primitive areas are managed to maintain natural processes and to protect key attributes like water quality, riparian and aquatic habitats, and natural stream flows. They also serve as refuges for many vulnerable fish and wildlife species.

    • South Fork of the Jocko Primitive AreaIn 1974, the Tribal Council set aside the South Fork of the Jocko Primitive Area as a recreational and cultural use area. In 1979 they restricted use of the area to Tribal members and their families, and in 1990, they expanded the area to include several drainages. Logging is no longer permitted in the area, although motorized vehicles are allowed on designated roads.
    • Mission Mountains Tribal Wilderness AreaEstablished in 1982, the Mission Mountains Tribal Wilderness encompasses 91,778 acres. About 20,500 acres of the wilderness lie within the Jocko Drainage. Motorized vehicles are not allowed in the wilderness and the area is managed to maintain its pristine character.
    • Show More