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Weiser River Subbasin

Data Details
Hydrologic Unit Code 17050124
Size 1,686 square miles (1,079,148 acres)

Water Bodies with EPA-Approved TMDLs (Category 4a)

Crane Creek, Little Weiser River, North and South Crane Creeks, Tennison Creek, Weiser River

Beneficial Uses Affected Cold water aquatic life, salmonid spawning, primary/secondary contact recreation, drinking water supply, wildlife, aesthetics
Major Land Uses Dryland and irrigated agriculture, range, forest, riparian, open water
Date Approved by EPA

January 2007
Approval Letter

Subbasin Characteristics

The Weiser River subbasin encompasses a large area in southwestern Idaho. The headwaters for the Weiser River originate in the southern end of the Seven Devil Mountain Range and the west-central mountains of Idaho. A majority of the population in the subbasin is associated with small homesteads. The municipalities of Weiser, Midvale, Cambridge, and Council are the only recognized urban areas in the subbasin.

2006 Subbasin Assessment and TMDL

Overall, 12 §303(d)-listed stream segments are within the Weiser River subbasin. Of these, 8 stream segments were determined not to be supporting their beneficial uses and/or exceeded water quality criteria and had TMDLs developed (including temperature TMDLs prepared in the addendum discussed below); 2 were determined to be intermittent water bodies and did not receive TMDLs; and 1 was determined to be fully supporting its beneficial uses and also did not receive a TMDL. Action on Crane Creek Reservoir will be deferred until 2007 to allow further study and to assess the status and appropriateness of its designated uses.

TMDLs were developed to address sediment and bacteria in the Weiser River subbasin. Additionally, total phosphorus load allocations have been established based on load allocations set in the Snake River-Hells Canyon subbasin assessment and total maximum daily loads.

2006 TMDL: Streams and Pollutants for Which TMDLs Were Developed

Stream Pollutants
Weiser River, Galloway Dam to mouth (at Snake River) Sediment, bacteria, total phosphorus
Weiser River, Little Weiser River to Galloway Dam Sediment, total phosphorus
Crane Creek Sediment, bacteria, total phosphorus
Little Weiser River Bacteria, sediment, total phosphorus

2006 Addendum

Five stream segments were placed on the 1998 §303(d) list of impaired waters by EPA for reasons associated with temperature criteria violations. Two stream segments were on the original 1998 list and three were added by EPA in 2001.This TMDL addendum presents loading analyses for the five temperature-listed segments in the subbasin, as well as for the Weiser River as a whole and ten of its major tributaries.

Effective shade targets were established for the Weiser River and ten associated tributaries based on the concept of maximum shading under potential natural vegetation resulting in natural background temperature levels. Shade targets were derived from effective shade curves developed for similar vegetation types in the Northwest. Existing shade was determined from aerial photo interpretation field verified with Solar Pathfinder data.

2006 Addendum: Streams and Pollutants for which TMDLs Were Developed

Stream Pollutants
Weiser River, Little Weiser River to Galloway Dam Temperature
Crane Creek, headwaters to mouth Temperature
Little Weiser River, headwaters to mouth Temperature
North Crane Creek, headwaters to mouth Temperature

Subbasin Document(s)

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DEQ Boise Regional Office
1445 N. Orchard St.
Boise, ID 83706
Ph: (208) 373-0550
Fax: (208) 373-0287
Toll Free: (888) 800-3480

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