Protecting Public Health and the Environment.

Snake River (Upper Snake-Rock) Subbasin

Subbasin at a Glance

Hydrologic Unit Code 17040212
Size 2,438 square miles (1,536,880 acres)

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

Billingsley Creek, Briggs Creek, Cedar Draw, Clear Creek, Clear Lakes, Clover Creek, Deep Creek, Dry Creek, McMullen Creek, Mud Creek, North/Dry Cottonwood Creek, Pioneer Reservoir, Riley Creek, Rock Creek, Sand Springs, Snake River and tributaries, tributaries to Yahoo and Deep Creeks, Vinyard Creek, West Fork Dry Creek

Beneficial Uses Affected Cold water aquatic life, salmonid spawning, primary and secondary contact recreation
Major Land Uses Rangeland, agriculture
Date Mid-Snake River TMDL Approved by EPA April 1997
EPA Approval Letter
Date Approved by EPA August 2000
EPA Approval Letter
Date Modification Approved by EPA September 2005
EPA Approval Letter
Date City of Twin Falls TSS Revision Approved by EPA

March 2011
EPA Approval Letter

Subbasin Characteristics

The Upper Snake-Rock subbasin is located in southern Idaho, primarily in Gooding, Jerome, and Twin Falls Counties. Over 95% of the subbasin is a Snake River Basin/High Desert ecoregion. Its topography consists of tablelands with medium to high relief, and its vegetation is made up predominantly of a sagebrush-grass zone with minimal riparian vegetation in the Middle Snake River or its tributaries. The land use in the subbasin is 54% desert shrublands (on which grazing is a major activity) and 41% agricultural land (both irrigated and dryland).

1999 Subbasin Assessment and TMDL

In the Upper Snake-Rock subbasin, 31 water bodies/stream segments were listed on the 1996 §303(d) list, including 10 segments of the middle Snake River. The TMDL covers 93 miles of the Snake River, including 28 named tributaries.

The middle Snake River TMDL, discussed below, also covers portions of this subbasin.

The middle Snake River is a managed water system where normal flow regimes are no longer present, which allows sediment to accumulate. In general, the middle Snake River and its tributaries are impacted by runoff from irrigated crop production, rangeland, pastureland, animal holding areas, feedlots, dredging, hydro-modification, and urban runoff. Natural springs have exhibited hydro-modification and streambank modification from activities relating to sedimentation, aquaculture, hydropower, irrigated crop production, and land development.

TMDLs were not written for ammonia, nitrogen, pesticides, oil and grease, or temperature. Data did not show that nitrogen, pesticides, or oil and grease were exceeding water quality standards or impacting beneficial uses. It is recommended that pesticides and oil and grease be removed from the §303(d) list; nitrogen levels will continue to be reviewed by DEQ. Clover Creek was found to be polluted by ammonia, but ammonia is not listed on the §303(d) list for Clover Creek. It is recommended that ammonia be added to the next §303(d) list for Clover Creek; a TMDL will be completed after this occurs. Temperature TMDLs have been deferred until after new water quality standards are developed for temperature.

1999 TMDL: Streams and Pollutants for Which TMDLs Were Developed

Alpheus Creek
Sediment (total suspended solids), phosphorus
Billingsley Creek
Sediment (total suspended solids), pathogens (fecal coliform bacteria), phosphorus
Blind Canyon Creek
Sediment (total suspended solids), pathogens (fecal coliform bacteria), phosphorus
Cedar Draw
Sediment (total suspended solids), pathogens (fecal coliform bacteria), phosphorus
Clear Springs
Sediment (total suspended solids), phosphorus
Clover Creek
Sediment (total suspended solids), pathogens (fecal coliform bacteria), phosphorus
Cottonwood Creek
Sediment (total suspended solids), pathogens (fecal coliform bacteria), phosphorus
Crystal Springs
Sediment (total suspended solids), phosphorus
Deep Creek
Sediment (total suspended solids), pathogens (fecal coliform bacteria), phosphorus
Dry Creek (2 segments)
Sediment (total suspended solids), pathogens (fecal coliform bacteria), phosphorus
Dry Creek (West Fork)
Sediment (total suspended solids), pathogens (fecal coliform bacteria), phosphorus
Ellison Creek
Sediment (total suspended solids), phosphorus
McMullen Creek
Sediment (total suspended solids), pathogens (fecal coliform bacteria), phosphorus
Mud Creek
Sediment (total suspended solids), pathogens (fecal coliform bacteria), phosphorus
Riley Creek
Sediment (total suspended solids), pathogens (fecal coliform bacteria), phosphorus
Rock Creek
Sediment (total suspended solids), pathogens (fecal coliform bacteria), phosphorus
Thousand Springs Creek
Sediment (total suspended solids), phosphorus
Vineyard Creek
Sediment (total suspended solids), phosphorus
Bliss Reservoir
Sediment (total suspended solids), pathogens (fecal coliform bacteria), phosphorus
Lower Salmon Falls Reservoir
Sediment (total suspended solids), pathogens (fecal coliform bacteria), phosphorus
Pioneer Reservoir
Sediment (total suspended solids), pathogens (fecal coliform bacteria), phosphorus
Shoshone Falls Reservoir
Sediment (total suspended solids), pathogens (fecal coliform bacteria), phosphorus
Upper Salmon Falls Reservoir
Sediment (total suspended solids), pathogens (fecal coliform bacteria), phosphorus
Middle Snake River (10 segments)
Sediment (total suspended solids), pathogens (fecal coliform bacteria), phosphorus

1997 Middle Snake River Watershed Assessment and TMDL

Watershed at a Glance

Hydrologic Unit Code 17040212 (Upper Snake-Rock Subbasin)
17040213 (Salmon Falls Subbasin)
Size 94 square miles (60,160 acres)
Beneficial Uses Affected Aquatic life, primary and secondary contact recreation
Major Land Uses Irrigated agriculture, confined animal feeding operations, food processing, aquaculture, urban, hydroelectric development

A large portion of the economy and culture of south-central Idaho is dependent on water provided by the middle Snake River and its tributaries. The middle Snake River has 14 segments listed as priority segments on the 1996 §303(d) list.

The middle Snake River's hydrologic system is shaped by precipitation, the river itself, tributaries, irrigation return flows, ground water flow, and geothermal sites. With the exception of precipitation, all of these sources receive nutrient inputs from human activities. Severely diminished instream flows have historically limited the middle Snake River's ability to assimilate these nutrient-rich inputs.

This document is the first phase in a phased TMDL and focuses on reductions in total phosphorus. Proposed industry total phosphorus reductions will be implemented within 5 years of the approval of this TMDL and will be maintained for an additional 5 years to reach an instream target of 0.75 milligrams per liter total phosphorus at Gridley Bridge in Hagerman, Idaho. Total phosphorus reductions will come from aquaculture, food processors, municipalities, confined animal feeding operations, irrigated agriculture, and the hydroelectric industry.

Additional phases of the phased TMDL focus on sediment reduction (phase II), nitrogen reduction (phase III), flow (phase IV), and other pollutants and stressors (phase V). These phases have been addressed simultaneously in the Upper Snake Rock TMDL.

1997 TMDL: Streams and Pollutant for Which TMDLs Were Developed

14 sections of the middle Snake River, including Bliss, Shoshone Falls, Upper Salmon Falls, and Lower Salmon Falls Reservoirs
Total phosphorus

Aquaculture Wasteload Allocations

Draft wasteload allocations for aquaculture facilities were developed in July 2004. These allocations are designed to meet the total phosphorus reductions as specified in the Middle Snake River and Upper Snake Rock TMDLs. The allocations affect 37 TMDLs for total phosphorus and total suspended solids and six associated segments of the Snake River.

Public comments were accepted on the document in August 2004. Based on the information and comments received, DEQ modified the document and resubmitted it for public comment in the following three parts:

Subbasin Documents


Staff Contacts

Water Quality Manager
Kiley Mulholland
DEQ Twin Falls Regional Office
650 Addison Avenue West, Suite 110
Twin Falls, ID 83301
(208) 736-2190
kiley.mulholland@deq.idaho.gov