Protecting Public Health and the Environment.

Boise River (South Fork) Subbasin

Subbasin at a Glance

Hydrologic Unit Code 17050113
Size 1,306 square miles (835,645 acres)

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

Lime Creek, Smith Creek and tributaries

Beneficial Uses Affected Aquatic life support, contact recreation, water supply, wildlife habitats, aesthetics

Major Land Uses

Predominantly uninhabited federal land managed by the US Forest Service; forestry, roads, mining, agriculture/livestock, recreation

Date Approved by EPA
(2002 subbasin assessment)

Subbasin assessment only; not subject to EPA approval
Date Approved by EPA
(2008 TMDL)

March 2009
EPA Approval Letter

Subbasin Characteristics

The South Fork Boise River subbasin is located in southwestern Idaho, east of Boise and predominantly in Elmore and Camas Counties. The watershed includes the South Fork Boise River upstream of the slack water of Arrowrock Reservoir, Anderson Ranch Reservoir, and all South Fork Boise River tributaries upstream to the headwaters. The subbasin area is primarily federally owned and administered. Prairie, Pine, and Featherville are the only recognized communities in the watershed that have year-round residents; second/summer/recreational homes are found in numerous subdivided areas throughout the watershed. Access is provided by many miles of US Forest Service-maintained roads and by county-owned or county-maintained roads.

2002 Upper Boise River Watershed Assessment

Watershed at a Glance

The Upper Boise River watershed is made up of two subbasins, as summarized in the table below.

Hydrologic Unit Codes

17050111 (North/Middle Fork Boise River Subbasin)
17050113 (South Fork Boise River Subbasin)


2,033 square miles (1,301,120 acres)

Beneficial Uses Affected

Cold water aquatic life, salmonid spawning, primary and secondary contact recreation, domestic water supply

Major Land Uses

Forestry, roads, mining, agriculture/livestock, recreation

Located in southwest Idaho, the upper Boise River watershed is about 2,033 square miles of predominantly undeveloped forestland and open range with both managed and free-flowing streams. The upper Boise River watershed is comprised of the two hydrologic cataloging units of the Boise River system upstream of Arrowrock Reservoir. The waters of the subbasin join to form the Arrowrock Reservoir, which supplies water to Lucky Peak Reservoir and the lower Boise River.

This subbasin assessment found that all §303(d)-listed water bodies within the upper Boise River watershed are currently fully supporting all of their beneficial uses and are no longer candidates for TMDL development.

The subbasin assessment also lists water bodies not fully supporting their beneficial uses that should be added to the §303(d) list during the next listing cycle.

2002 Summary of Assessment Outcomes

On 1998 §303(d) List

Buck Creek
          Delist; no TMDL needed
Browns Creek
          Delist; no TMDL needed
Willow Creek
          Delist; no TMDL needed
South Fork Boise River
          Delist; no TMDL needed
Deer Creek
          Delist; no TMDL needed
Little Smoky Creek
          Delist; no TMDL needed
Cayuse Creek
          Delist; no TMDL needed
North Fork Feather Creek
          Delist; no TMDL needed
Smith Creek
          Delist; no TMDL needed
Rattlesnake Creek
          Delist; no TMDL needed

Not on 1998 §303(d) List

Crooked River
          Add to §303(d) list for sediment
Beaver Creek
          Add to §303(d) list for sediment
Rabbit Creek
          Add to §303(d) list for unknown pollutant
Meadow Creek
          Add to §303(d) list for sediment
French Creek
          Add to §303(d) list for sediment
Little Camas Reservoir
          Add to §303(d) list for sediment

2008 Subbasin Assessment and TMDL

The subbasin consists of 34 separate water body assessment units. Of these, 14 were identified as water quality limited and were placed on the 2002 §303(d) list. Of these, 5 (listed below) are identified in the subbasin assessment as needing TMDLs to address temperature. Temperature is a water quality factor integral to the lifecycle of fish and other aquatic species. Elevated stream temperatures can be harmful to fish at all life stages. Sources of elevated temperature are anthropogenic alterations related to roads, farming, grazing, mining, timber harvest, community or domestic development, or other activities that reduce stream shade or alter the stream in a way that results in increased stream temperatures.

In addition, the subbasin assessment identifies several streams to be added to the state's list of impaired water bodies for flow and habitat alteration in the next Integrated Report and others to be removed for sediment and unknown pollutants.

2008 TMDL: Streams and Pollutants for Which TMDLs Were Developed

Smith Creek
Lime Creek
North Fork Lime Creek
Middle Fork Lime Creek
South Fork Lime Creek

Subbasin Documents

Staff Contacts

Surface Water Quality Manager
Lance Holloway
DEQ Boise Regional Office
1445 N. Orchard St.
Boise, ID 83706
(208) 373-0550

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