Official Government Website

Little Lost River Subbasin

Data Details
Hydrologic Unit Codes 17040217
Size 963 square miles (616,320 acres)
Water Bodies with EPA-Approved TMDLs (Category 4a) Little Lost River, Main Fork, Sawmill Creek, Wet Creek
Beneficial Uses Affected Cold water aquatic life, salmonid spawning
Major Land Uses Forestry, agriculture
Date Approved by EPA September 2000
EPA Approval Letter
Date 2015 Temperature Addendum Approved by EPA January 2016
EPA Approval Letter

Subbasin Characteristics

The Little Lost River subbasin is located in eastern Idaho on the northern margin of the Snake River plain. The subbasin is approximately 50 miles long by 20 miles wide (963 square miles). The valley floor averages 7 miles wide and is fairly consistent in width from the head of the valley to the mouth. Shaped like a long rectangle, the high-elevation valley is flanked by the Lost River Range to the west and the Lemhi Range to the east.

2000 Subbasin Assessment and TMDL

Water quality, native fish populations, and riparian habitat conditions have been issues of concern in the Little Lost River subbasin since the combined effects of flooding, wildfires, warm season grazing, exotic species, and human-made diversions have combined to alter sediment deposition, fish populations, and riparian vegetation along the listed segments.

The listed segments are also important components of the Little Lost River Bull Trout recovery unit. The Endangered Species Act requires that conservation plans be developed and implemented to restore Bull Trout populations to levels that ensure their persistence in the Little Lost River subbasin.

DEQ has determined that water quality has been limited by sediment deposition and elevated stream temperatures due to streambank erosion and reduction of riparian vegetation.

DEQ has developed recommendations for reducing streambank erosion that will ultimately result in beneficial use support through improving streambank stability and subsequently riparian vegetation to reduce temperature. Sediment load reductions are quantified through streambank erosion inventories that estimate streambank erosion based on bank conditions documented along several reaches of each stream. Instream sediment targets have been identified from literature values that are supportive of salmonid spawning and cold water biota. These target values will be used to track the progress of streambank recovery and determine the need for additional management practices to improve water quality. Monitoring will be conducted by land management agencies to determine the adequacy of reductions and management practices.

2000 TMDL: Streams and Pollutants for Which TMDLs Were Developed

Stream Pollutants
Little Lost River Sediment
Sawmill Creek Sediment
Wet Creek Sediment

Subbasin Document(s)

This accordion will not appear on the screen

DEQ Idaho Falls Regional Office
900 N. Skyline Drive, Suite B
Idaho Falls, ID 83402
Ph: (208) 528-2650
Fax: (208) 528-2695
Toll Free: (800) 232-4635

ver: 3.5.2 | last updated:
Jump back to top of page button