Section 303(d) of the Clean Water Act requires states and tribes to identify and prioritize water bodies that do not meet water quality standards through Idaho’s Integrated Report. Idaho must develop a water quality improvement plan, called a total maximum daily load (TMDL), for those water bodies not meeting water quality standards. A subbasin assessment is the first step toward developing a TMDL.
Subbasin Assessments and TMDLs
In Idaho, TMDLs are developed on a subbasin level, which means water bodies and pollutants within a hydrologic subbasin are generally addressed in a single document. A subbasin is based on a cataloging unit of the US Geological Survey (USGS) (i.e., a subbasin is the same as a USGS 4th-field hydrologic unit code or HUC). Idaho has 86 subbasins (HUCs) entirely or partially within its borders.
Five-Year Reviews
Five-year reviews address the water bodies in a subbasin that are in Category 4a of Idaho’s most recent Integrated Report. Five-year reviews outline the appropriateness of beneficial uses, water quality criteria, TMDL targets, pollutant allocations, and other assumptions of the TMDL. The review describes current water quality status, pollutant sources, and recent pollution control efforts in the subbasin. The 5-year review process may also recommend delistings or TMDL revisions to incorporate updated information.
TMDL Implementation Plans
Subbasin Assessments, Five-Year Reviews, and Implementation
| Subbasin Name | Hydrologic Unit Code (HUC) | TMDL Status | Implementation Plan Status | Five-Year Review Status |
|---|---|---|---|---|
| American Falls Subbasin | 17040206 | Approved by EPA August 2012 | Agriculture completed May 2014 | |
| Bear River Basin/Malad River Subbasin | 16010201 16010102 16010204 16010202 | Approved by EPA June 2006 Bear River Basin Addendum approved by EPA September 2013 | Lower Bear/Malad Subbasin Agriculture completed May 2010 Central Bear (Bear River Main Stem) Agriculture completed October 2008 Northern Middle Bear Agriculture completed September 2008 Southern Middle Bear Agriculture completed September Bear Lake Subbasin Agriculture completed July 2008 Bear River/Malad River Forest Svc. completed April 2008 Daniels Watershed completed 2007 Cub River Watershed Agriculture completed September 2006 | Completed January 2017 |
| Beaver-Camas Subbasin | 17040214 | Approved by EPA August 2005 TMDL and Five-Year Review September 2022 | Under development | Completed September 2022 |
| Big Lost River Subbasin | 17040218 | Approved by EPA August 2004 Addendum approved by EPA December 2011 2019 Addendum and Five-Year Review approved by EPA June 2019 | Agriculture completed May 2011 | See TMDL Addendum |
| Big Wood River Subbasin | 17040219 | Approved by EPA May 2002 Errata approved by EPA February 2012 Temperature Addendum approved by EPA December 2013 | Agriculture completed October 2006, revised February 2014 | Completed December 2017 |
| Birch Creek Subbasin | 17040216 | Assessment completed March 2005 | ||
| Blackfoot River Subbasin | 17040207 | Approved by EPA April 2002 Brush Creek Temperature TMDL approved by EPA November 2007 Blackfoot River TMDL Addendum approved by EPA October 2013 | Completed February 2006 | Completed August 2015 |
| Boise – Mores Creek Subbasin | 17050112 | Approved by EPA February 2010 | Sediment and E. coli completed May 2019 | |
| Boise River (Lower) Subbasin | 17050114 | Approved by EPA January 2000 Assessments completed December 2001 Addendum approved by EPA June 2008 Lake Lowell TMDL approved by EPA December 2010 Sediment and Bacteria Addendum approved by EPA September 2015 Total Phosphorus Addendum approved by EPA December 2015 | Completed December 2003 Phosphorus completed December 2008 Lake Lowell completed June 2012 | Completed February 2009 |
| Boise River (North/Middle Fork) Subbasin | 17050111 | Assessment completed November 2002 | NA | |
| Boise River (South Fork) Subbasin | 17050113 | Assessment completed 2002 TMDL approved by EPA March 2009 | See TMDL Appendix J | See TMDL |
| Brownlee Reservoir Subbasin includes Wildhorse River watershed | 17050201 | Approved by EPA November 2003 Wildhorse River TMDL approved by EPA October 2007 Weiser Flats TMDL approved by EPA July 2021 | Agriculture completed September 2004, revised 2014 Wildhorse River Agriculture completed March 2010 Wildhorse River Forestry completed February 2010 | Weiser Flat completed August 2015 Wildhorse River completed August 2015 |
| Bruneau River Subbasin | 17050102 | Approved by EPA March 2001 Jacks Creek Aquaculture Addendum TMDL approved by EPA November 2007 | Bruneau River Agriculture completed June 2002, revised March 2013 Jacks Creek Agriculture completed June 2002, revised March 2013 | |
| C.J. Strike Reservoir Subbasin | 17050101 | Approved by EPA June 2006 | Agriculture completed November 2007 Dissolved Oxygen completed November 2007, revised December 2008 | |
| Camas Creek Subbasin | 17040220 | Approved by EPA September 2005 2016 Temperature Addendum approved by EPA December 2016 | Agriculture completed August 2007, revised March 2013 | Completed December 2016 |
| Clark Fork River (Lower) Subbasin | 17010213 | Clark Fork/Pend Oreille TMDL approved by EPA September 2000 and April 2001 Lower Clark Fork TMDL approved by EPA October 2007 | Agriculture completed September 2014 | |
| Clearwater River (South Fork) Subbasin includes Cottonwood Creek watershed | 17060305 | Cottonwood Creek TMDL approved by EPA June 2000 and March 2004 | Completed April 2006 Agriculture completed March 2005, revised January 2014 | 2021 Cottonwood Creek Ammonia Review |
| Clearwater River Subbasin includes Hatwai Creek, Jim Ford Creek, Lindsay Creek, Lolo Creek tributaries, Potlatch River, Winchester Lake-Lapwai Creek watersheds | 17060306 | Winchester Lake TMDL approved by EPA March 1999 Jim Ford Creek TMDL approved by EPA June 2000 Lindsay Creek TMDL approved by EPA June 2007 Potlatch River TMDL approved by EPA February 2009 Hatwai Creek TMDL approved by EPA December 2010 Lolo Creek Tributaries TMDL approved by EPA December 2011 Jim Ford Creek Temperature TMDL approved by EPA September 2018 Potlatch River Watershed TMDL approved by EPA July 2018 Hatwai Creek Temperature TMDL approved by EPA August 2018 | Winchester Lake completed May 2000 Lindsay Creek Agriculture completed April 2008 Potlatch River revised March 2013 Jim Ford Creek Agriculture revised February 2014 Jim Ford Creek Agriculture Addendum October 2016 Potlatch River Agriculture Addendum | Potlatch River completed October 2017 |
| Clearwater River, North Fork (Upper) Subbasin | 17060307 | Approved by EPA December 2003 Lake Creek Temperature TMDL approved by EPA September 2018 | Under development | |
| Clearwater River, North Fork (Lower) Subbasin | 17060308 | Approved by EPA January 2003 Five-Year Review and TMDL Addendum approved by EPA November 2013 | Completed May 2004 Addendum completed December 2013 | See 2013 TMDL Addendum |
| Coeur d’Alene Lake Subbasin includes Black Lake watershed | 17010303 | Approved by EPA July 2000 Black Lake TMDL approved by EPA August 2011 Coeur d’Alene Lake Tributaries Addendum approved by EPA November 2012 Fernan Lake Addendum approved by EPA November 2013 | Completed 2002 | See 2011 TMDL Addendum and Update |
| Coeur d’Alene River (South Fork) Subbasin | 17010302 | Approved by EPA August 2003 | Under development | |
| Coeur d’Alene River (Upper/North Fork) Subbasin | 17010301 | Approved by EPA February 2002 Addendum approved by EPA April 2014 | Under development | See North Fork Coeur d’Alene River Subbasin Watershed Restoration Effectiveness Review – Sediment Reductions and Biological Response Document and Success Story |
| Curlew Valley Subbasin | 16020309 | Approved by EPA July 2019 | ||
| Goose Creek Subbasin | 17040211 | Approved by EPA July 2004 Temperature Addendum approved by EPA April 2012 | Under development | Completed June 2010 |
| Hangman Creek Subbasin | 17010306 | Approved by EPA September 2007 | ||
| Henrys Fork (Upper and Lower) Subbasin | 17040202 17040203 | Assessment completed December 1998 Addendum approved by EPA August 2010 E. Coli TMDL approved by EPA March 2021 | NA | Completed April 2010 Completed May 2017 |
| Idaho Falls Subbasin | 17040201 | Approved by EPA November 2004 | Under development | |
| Jordan Creek Subbasin | 17050108 | Partially approved/partially disapproved by EPA April 2011 | ||
| Kootenai and Moyie Rivers Subbasins | 17010101 17010104 17010105 | Approved by EPA January 2007 2014 Temperature TMDL Addendum approved by EPA October 2014 2019 Temperature TMDL Addendum approved by EPA June 2019 | Draft completed November 2005 | |
| Lemhi River Subbasin | 17060204 | Approved by EPA March 2000 Addendum approved by EPA February 2013 | Completed September 2001 | See October 2012 TMDL Addendum |
| Little Lost River Subbasin | 17040217 | Approved by EPA September 2000 2015 Temperature Addendum approved by EPA January 2016 | Completed February 2002 | Completed July 2015 |
| Little Salmon River Subbasin | 17060210 | Approved by EPA March 2006 Addendum approved by EPA April 2013 | Completed November 2008 Agriculture Implementation Plan April 2016 | Completed April 2012 |
| Little Wood River Subbasin | 17040221 | Approved by EPA September 2005 | Agriculture completed March 2010 | |
| Lochsa River Subbasin | 17060303 | Assessment completed September 1999 Addendum submitted to EPA May 2012 Temperature TMDL approved by EPA August 2018, revised August 2020 | NA | |
| Medicine Lodge Creek Subbasin | 17040215 | Approved by EPA May 2003 2016 Addendum approved by EPA January 2017 | Agriculture completed July 2002 | |
| Owyhee River (Middle) Subbasin | 17050107 | Approved by EPA February 2000 Watershed Temperature TMDLs approved by EPA July 2012 | Completed February 2002 Agriculture Implementation Plan May 2017 | Completed June 2009 |
| Owyhee River (South Fork) Subbasin | 17050105 | Approved by EPA March 2000 Watershed Temperature TMDLs approved by EPA July 2012 | Agriculture Implementation Plan May 2017 | |
| Owyhee River (Upper) Subbasin | 17050104 | Approved by EPA March 2003 Watershed Temperature TMDLs approved by EPA July 2012 | Agriculture completed October 2004 Agriculture Implementation Plan May 2017 | Completed June 2009 |
| Pahsimeroi River Subbasin | 17060202 | Approved by EPA December 2001 Addendum approved by EPA April 2014 | Agriculture completed September 2005 | See 2013 TMDL Addendum |
| Palisades Subbasin includes Fall Creek watershed | 17040104 | Approved by EPA February 2001 Fall Creek TMDL approved by EPA April 2004 2013 Addendum and Five-Year Review approved by EPA February 2014 Rainey Creek TMDL approved by EPA July 2019 | Completed August 2002 | See 2013 TMDL Addendum submitted to EPA June 2019 |
| Palouse River Subbasin includes Cow Creek and Paradise Creek watersheds | 17060108 | Paradise Creek TMDL approved by EPA February 1998 Palouse River Tributaries TMDL approved by EPA March 2005 Cow Creek TMDL approved by EPA February 2006 South Fork Palouse River TMDL approved by EPA October 2007 Cow Creek TMDL Addendum approved Paradise Creek TMDL 2015 Bacteria Addendum approved by EPA November 2016 Palouse River Subbasin 2017 Temperature TMDL approved by EPA August 2017 | Paradise Creek completed December 1999 Cow Creek Agriculture revised May 2013 Cow Creek Temperature July 2014 Palouse River Agriculture Addendum July 2016 | Completed December 2015 |
| Payette River (Middle Fork) Subbasin | 17050121 | Approved by EPA July 2000 Temperature TMDL approved by EPA December 2007 | Completed August 2003 | Completed February 2009 |
| Payette River (North Fork) Subbasin includes Cascade Reservoir watershed | 17050122 17050123 | Cascade Reservoir Phase I approved by EPA May 1996 Cascade Reservoir Phase II approved by EPA April 1999 North Fork Payette River TMDL approved by EPA August 2005 Cascade Reservoir Tributary Addendum approved by EPA February 2012
| Cascade Reservoir all phases completed June 2000 North Fork Payette River | Cascade Reservoir all phases North Fork Payette River completed July 2012 Cascade Reservoir Watershed completed February 2018 |
| Payette River (South Fork) Subbasin | 17050120 | Assessment completed July 2005 | NA | Completed January 2011 |
| Payette River Subbasin includes Bissel Creek watershed | 17050122 | Lower Payette River TMDL approved by EPA May 2000 Bissel Creek TMDL approved by EPA October 2003 Big Willow Creek Addendum approved by EPA July 2008 Little Willow Creek Addendum approved by EPA December 2013 | Completed January 2003 Big Willow completed August 2010 Bissel Creek completed April 2006, revised 2014 Little Willow completed June 2014 | Completed February 2010 |
| Pend Oreille Lake Subbasin | 17010214 | Clark Fork-Pend Oreille TMDL approved by EPA September 2000 and April 2001 Nearshore Waters TMDL approved by EPA October 2002 Temperature TMDL Addendum approved by EPA April 2008 Sediment TMDL Addendum approved by EPA January 2008 Pack River Nutrients TMDL Addendum approved by EPA December 2008 | Nearshore Waters completed December 2004 Pack River completed July 2006 Cocolalla Lake, Cocolalla Creek, and Hoodoo Creek completed July 2004 | Completed June 2015 Pend Oreille Lake and River Tributaries completed April 2017 |
| Portneuf River Subbasin | 17040208 | Approved by EPA April 2001 Revision and Addendum approved by EPA August 2010 | Updated June 2020 | See Revised TMDL |
| Priest River Subbasin | 17010215 | Approved by EPA March 2002 Addendum approved by EPA June 2003 2016 Temperature Addendum approved by EPA May 2019 | Under development | |
| Raft River Subbasin | 17040210 | Approved by EPA July 2004 Temperature Addendum approved by EPA April 2012 | Agriculture completed July 2006 | Completed September 2011 |
| Salmon Falls Creek Subbasin | 17040213 | Mid-Snake River TMDL approved by EPA April 1997 Mid-Snake River TMDL Modification approved by EPA 2005 Salmon Falls Creek TMDL approved by EPA February 2008 Salmon Falls Creek TMDL approved by EPA October 2021 | Upper Snake Rock June 2001 Agriculture completed February 2009 | Completed November 2022 |
| Salmon River (Lower) and Hells Canyon Subbasins | 17060209 17060101 | Approved by EPA February 2010 | ||
| Salmon River (Middle) – Chamberlain Creek Subbasin | 17060207 | Approved by EPA January 2003 | Under development | 2017 Temperature TMDL and Five-Year Review approved by EPA August 2017 |
| Salmon River (Middle) – Panther Creek Subbasin | 17060203 | Approved by EPA July 2001 | Completed November 2002 | |
| Salmon River (South Fork) Subbasin | 17060208 | Approved by EPA January 1992 Addendum approved by EPA October 2012 | Under development | Completed March 2011 |
| Salmon River (Upper and Lower Middle Forks) Subbasin | 17060205 17060206 | Approved by EPA February 2009 | ||
| Salmon River (Upper) Subbasin | 17060201 | Approved by EPA March 2003 2016 Addendum and Five-Year Review approved by EPA December 2016 | Agriculture completed February 2007 | |
| Salt River Subbasin | 17040105 | 2015 E. coli TMDL approved by EPA January 2018 and August 2018 | Agriculture completed July 2020 | |
| Selway River (Lower) Subbasin | 17060302 | Subbasin assessment December 2000 | NA | |
| Snake (Lower)-Asotin Subbasin includes Tammany Creek watershed | 17060103 | Approved by EPA February 2002 Addendum approved by EPA December 2010 | Under development | |
| Snake River – Hells Canyon Subbasins | 17060101 17050103 17050115 17050201 | Approved by EPA September 2004 | See TMDL for Implementation Strategies | |
| Snake River (Middle) – Succor Creek Subbasin | 17050103 | Approved by EPA January 2004 Addendum approved by EPA December 2007 Tributaries Sediment TMDL Addendum approved by EPA October 2013 | Completed July 2005, revised 2014 | Completed September 2011 |
| Snake River (Upper Snake-Rock) Subbasin | 17040212 | Mid-Snake TMDL Phase I approved by EPA April 1997 Upper Snake Rock TMDL approved by EPA August 2000 Upper Snake Rock TMDL Modification approved by EPA September 2005 City of Twin Falls TSS Revision approved by EPA March 2011 | Completed June 2001 | Completed April 2010 |
| Spokane River (Upper) Subbasin | 17010305 | Approved by EPA January 2001 Fish Creek Watershed Assessment and TMDLs approved by EPA June 2008 | Under development | |
| St. Joe River Subbasin includes St. Maries River watershed | 17010304 | Approved by EPA August 2003 Temperature TMDL Addendum approved by EPA December 2011 | Agriculture completed November 2003 | Completed September 2011 |
| Teton River Subbasin | 17040204 | Approved by EPA February 2003, September 2003, February 2017 | Agriculture completed April 2005, revised February 2014 | |
| Walcott Lake Subbasin | 17040209 | Approved by EPA June 2000 Fall and Rueger Springs Creeks Aquaculture Addendum TMDLs approved by EPA March 2007 Lake Walcott TMDL 2013 Addendum: Marsh Creek approved by EPA January 2015 | Completed December 2001 | Completed May 2012 Completed October 2019 |
| Weiser River Subbasin | 17050124 | Approved by EPA January 2007 Temperature Addendum approved by EPA January 2007 | Agriculture revised May 2013 | Completed June 2014 |
| Willow Creek Subbasin | 17040205 | Approved by EPA June 2004 | Agriculture completed January 2011 |
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Water Quality Coordinator