|Hydrologic Unit Code||17040214|
|Size||1,005 square miles (643,083 acres)|
|Water Bodies with EPA-Approved TMDLs (Category 4a)||Beaver Creek, Camas Creek, Ching Creek, Crooked/Crab Creek, East and West Camas Creeks, Huntley Canyon Creek, Pleasant Valley Creek, Rattlesnake Creek, Threemile Creek, Warm Creek|
|Beneficial Uses Affected||Cold water aquatic life, salmonid spawning, primary/secondary contact recreation, domestic water supply|
|Major Land Uses||Range, irrigated agriculture, forestry|
|Date Approved by EPA||August 2005|
|Date Approved by EPA||September 2022|
The Beaver-Camas subbasin of southeastern Idaho is a watershed of the Upper Snake River Basin. The watershed is the easternmost in a series of five “sinks drainages.” The subbasin is dominated by both natural and human-caused flow alterations.
2005 Subbasin Assessment and TMDL
Data have been collected and analyzed to evaluate the scope of the water quality limiting issues on § 303(d)-listed and unlisted streams. Seven temperature TMDLs and one sediment TMDL have been developed in response to the data. Some TMDLs have been established for unlisted streams since water quality data show exceedances of Idaho’s water quality standards.
Streambank erosion, reduced riparian vegetation, and low flow conditions are the causes of increased water temperatures in the subbasin. Riparian grazing is the principal source of temperature and sediment load to the watershed. Elevated temperatures from reduced riparian vegetation and accelerated streambank erosion have been exacerbated by an ongoing drought.
There are two § 303(d)-listed segments on Beaver Creek. Temperatures in the upper segment of the creek exceed the state standard and a TMDL was developed. Perennial flows are seldom seen in the lower segment; therefore, it is proposed to be delisted for all currently listed pollutants and relisted only as flow altered.
Camas Creek is § 303(d) listed from its headwaters to its mouth (as two segments). Riparian grazing has contributed to bank erosion and elevated stream temperatures. Sediment and temperature TMDLs have been calculated to address the pollutants of concern in the upper segment. The lower segment of Camas Creek is intermittent and flow altered for irrigation; therefore, it is recommended this segment be listed only as flow altered. No TMDLs were developed for the lower segment.
Cow Creek is § 303(d) listed but is an ephemeral stream and should be delisted; ephemeral streams are not expected to support the same biological communities as perennial waters.
Dairy, East Fork Camas, Modoc, Threemile, and West Fork Camas Creeks are not § 303(d) listed. However, stream temperature data show major exceedances in Idaho’s numeric temperature criteria in these creeks. Temperature TMDLs were established for all five streams.
TMDLs were not developed for streams listed as flow or habitat altered. EPA does not believe that flow or habitat alteration are pollutants 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 or habitat altered streams.
2005 TMDL: Streams and Pollutants for Which TMDLs Were Developed
|Camas Creek||Sediment, temperature|
|East Fork Camas Creek||Temperature|
|West Fork Camas Creek||Temperature|
2022 TMDL and Five-Year Review
In the 2022 Beaver-Camas TMDL and Five-Year Review, 12 new TMDLs were developed for Assessment Units (AUs) listed as Category 5 in the 2022 Integrated Report. The causes include temperature (4 AUs), E. coli (7 AUs), and sedimentation/siltation (1 AU). In addition, 16 existing temperature TMDLs were updated, and these waterbodies remain in Category 4a.
2022 TMDL: Streams and Pollutants for Which TMDLs Were Developed
|Ching Creek||E. coli|
|East Camas Creek||E. coli|
|West Camas Creek||E. coli|
|Threemile Creek||E. coli|
|Beaver Creek||E. coli, sedimentations/siltation|
|Pleasant Valley Creek||E. coli, temperature|