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Big Wood River Subbasin

Hydrologic Unit Codes17040219
Size1,496 square miles (957,495 acres)
Water Bodies with EPA-Approved TMDLs (Category 4a)Big Wood River, Croy Creek, Eagle Creek, East Fork Wood River, Greenhorn Creek, Lake Creek, Magic Reservoir, Malad River, Quigley Creek, Rock Creek, Seamans Creek, Thorn Creek, Warm Springs Creek
Beneficial Uses AffectedCold water aquatic life, salmonid spawning, primary and secondary contact recreation, drinking water supply
Major Land UsesRange, forest, agriculture
Date Approved by EPAMay 2002
Approval Letter
Date Errata Approved by EPAFebruary 2012
EPA Approval Letter
Date Tributaries Temperature Addendum Approved by EPADecember 2013
EPA Approval Letter

Subbasin Characteristics

The Big Wood River subbasin is located in south-central Idaho and is made up of three elevation-ecological areas in Blaine, Gooding, Lincoln, and Camas Counties. These areas include the Sawtooth National Forest (above 5,800 feet in elevation), the Wood River Valley (4,000–5,800 feet in elevation), and the agricultural area (below 4,000 feet elevation). The Wood River Valley has atypical ecological characteristics of the lower elevation area. All physical and biological characteristics of the Big Wood River subbasin are related to these elevation-ecological areas.

2002 Subbasin Assessment and TMDL

The overall purpose of this subbasin assessment and TMDL is to characterize and document pollutant loads within the Big Wood River subbasin. Twenty stream segments on the § 303(d) list were evaluated; an additional four stream segments that were not on the § 303(d) list were also evaluated.

The document recommends that four streams (Horse Creek, Owl Creek, Baker Creek, and East Fork Wood River) be removed from the § 303(d) list. These streams are meeting their beneficial uses and/or state water quality standards.

The document also recommends two additional stream segments be listed on the next § 303(d) list. The first is in the Big Wood River main stem from Base Line to Magic Reservoir. The second is in the Big Wood River main stem from Interstate 84 to the Snake River (or the Malad River).

TMDLs were established for sediment, nutrients, and bacteria. Flow alteration will be evaluated further. A TMDL was not being established at this time for streams polluted by nitrite + nitrate. Temperature and dissolved oxygen TMDLs will be deferred until 2003 pending collection of more information. A TMDL was not established for turbidity at this time since the sediment TMDLs will create reductions in turbidity. The TMDL recommends that ammonia be delisted as a pollutant of concern.

2002 TMDL: Streams and Pollutants for Which TMDLs Were Developed

Stream Pollutants
Big Wood River Sediment, nutrients, bacteria
Eagle Creek Sediment, nutrients
Lake Creek Nutrients
Placer Creek Nutrients
Cove Creek Temperature
Greenhorn Creek Sediment, nutrients
Quigley Creek Sediment, nutrients
Seamans Creek Sediment, nutrients
Rock Creek Sediment, nutrients, bacteria
East Fork Rock Creek Sediment, nutrients
Thorn Creek Sediment, nutrients

2011 Errata to the Big Wood River Watershed Management Plan

This document corrected calculation errors in four tables that appeared in the final Big Wood River Watershed Management Plan (a total maximum daily load, or TMDL), approved by the US Environmental Protection Agency (EPA) on May 15, 2002. The calculation errors were a result of not using the correct design flow capacity for three wastewater treatment plants (WWTPs). The errors did not come to light until a National Pollutant Discharge Elimination System (NPDES) draft permit reissuance for the City of Hailey. The City of Ketchum and the Meadows WWTPs were also affected. DEQ and EPA recognized the errors and DEQ corrected Table H, page xviii; Table XX, page 64; Table HHH, page 76; and Table PPP, page 89. The revised tables are included in this errata and supersede those in the 2002 TMDL.

2013 Addendum

This document addresses three water bodies in the Big Wood River subbasin that have been placed in Category 5 of the 2010 Integrated Report for temperature impairment. Temperature TMDLs were developed for two of these water bodies: Quigley Creek and Rock Creek. Effective target shade levels were established for Quigley Creek and Rock Creek based on the concept of maximum shading under potential natural vegetation resulting in natural background temperature levels. Black Canyon Creek was found to have insufficient water to be assessed. No sources or pathways of pollutants were identified for Black Canyon Creek and the two assessment units of this water body are proposed for delisting in the next Integrated Report cycle.

2013 Addendum: Streams and Pollutants for Which TMDLs Were Developed

Stream Pollutants
Quigley Creek Temperature
Rock Creek Temperature

Subbasin Documents

Data Details
Hydrologic Unit Code 17040206
Size 2,869 square miles (1.8 million acres)
Beneficial Uses Affected 607 square miles (388,587 acres)
Major Land Uses Range, forest, agriculture, recreation
Date Approved by EPA Subbasin assessment only; not subject to EPA approval

Subbasin Characteristics

The American Falls subbasin covers 2,869 square miles in southeastern Idaho—much of which is within the Fort Hall Indian Reservation. American Falls Reservoir is the predominant water body in the subbasin and provides both irrigation water and electricity.

2012 Subbasin Assessment and TMDL

TMDLs were developed for nutrients on 17 water bodies in the subbasin and for sediment on 9 water bodies. TMDLs were also developed for nutrients and sediment for six point sources of pollution. Two of the point source wasteload allocations (sediment from the city of Blackfoot’s storm water runoff and nutrients from the Aberdeen wastewater treatment plant) require a reduction from current estimated wasteloads.

American Falls Reservoir and McTucker Creek are § 303(d) listed for flow alteration. However, the US Environmental Protection Agency does not believe that flow alteration is a pollutant as defined by the Clean Water Act. Since TMDLs are not required for water bodies impaired by pollution but not pollutants, TMDLs were not developed for flow alteration.

TMDLs were also not established for dissolved oxygen or bacteria. Dissolved oxygen was listed for the Snake River and American Falls Reservoir. Data did not indicate dissolved oxygen was a problem in the Snake River, and it was assumed that a nutrient TMDL will bring dissolved oxygen levels in the reservoir into compliance with water quality standards. Insufficient data existed to determine if bacteria impair recreation in Bannock Creek, so more data will be collected to determine beneficial use support.

The July 2006 analysis recommended that American Falls Reservoir be delisted for sediment and the Snake River be delisted for dissolved oxygen and nutrients. It is anticipated that American Falls Reservoir and the Snake River will be listed for temperature on future § 303(d) lists. The document also recommended that Danielson Creek, Hazard Creek (Little Hole Draw), and Sunbeam Creek be added to future § 303(d) lists.

In March 2009, the document was revised as a requirement of a contested case settlement agreement between J.R. Simplot, the City of Pocatello, and DEQ. Changes to the plan include the following:

  • Removal of nitrogen allocations for tributaries and point sources
  • Adoption of a tiered phosphorus target to achieve water quality standards and support beneficial uses with an interim phosphorus target of 0.07 mg/L total phosphorus
  • Ability to allow water pollutant trading and develop a trading framework if pollutant trading is deemed viable in the watershed

Additionally, in 2012, total phosphorus wasteload allocations for two conservation fish hatcheries (Idaho Department of Fish and Game’s Springfield Hatchery and the Shoshone-Bannock Tribes’ Crystal Springs Hatchery) were included based on a placeholder allocation remaining from historical operations at the Crystal Springs aquaculture facilities near Springfield. These hatchery operations are an important component to the State of Idaho and tribes’ efforts to restore endangered Sockeye and Chinook Salmon in central Idaho.

2012 TMDL: Streams and Pollutants for Which TMDLs Were Developed


American Falls ReservoirNutrients (total phosphorus)
Snake RiverNutrients (total phosphorus), sediment
Bannock Creek (includes Knox Creek)Nutrients (total phosphorus), sediment
Moonshine CreekSediment
Rattlesnake CreekSediment
West Fork Bannock CreekSediment
McTucker CreekNutrients (total phosphorus), sediment
Danielson CreekNutrients (total phosphorus), sediment
Hazard Creek (Little Hole Draw)Nutrients (total phosphorus), sediment
Sunbeam CreekNutrients (total phosphorus), sediment
Clear CreekNutrients (total phosphorus)
Seagull Bay TributaryNutrients (total phosphorus)
Spring CreekNutrients (total phosphorus)
Cedar SpillwayNutrients (total phosphorus)
Colburn WastewayNutrients (total phosphorus)
Crystal SpringsNutrients (total phosphorus)
Nash SpillNutrients (total phosphorus)
R SpillNutrients (total phosphorus)
Spring HollowNutrients (total phosphorus)
Sterling WastewayNutrients (total phosphorus)
Portneuf River (on the § 303(d) list for its own subbasin; Portneuf River TMDL already approved)Nutrients (total phosphorus)

Subbasin Documents

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DEQ Twin Falls Regional Office
650 Addison Avenue West, Suite 110
Twin Falls, ID 83301
Ph: (208) 736-2190
Fax: (208) 736-2194
Toll Free: (800) 270-1663

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