Owyhee (Upper) Subbasin

Subbasin at a Glance

Hydrologic Unit Code	17050104
Size	1,384,288 acres (total) 1,012,411 acres (in Idaho)
§303(d) Listed Stream Segments	Deep, Pole, Castle, Battle, Shoo Fly, Red Canyon, and Nickel Creeks; Blue Creek and Juniper Basin Reservoirs
Beneficial Uses Affected	Cold water aquatic life, salmonid spawning, primary and secondary contact recreation
Pollutants of Concern	Sediment, bacteria, flow alteration, temperature
Major Land Uses	Rangeland, riparian, forestry, irrigated agriculture
Date Approved by U.S. EPA	March 2003

Overview

The Upper Owyhee Subbasin encompasses a large area in southwest Idaho. The headwaters for the Owyhee River (East Fork) originate in northeast Nevada in the Independence Mountains.

Through the Upper Owyhee Watershed subbasin assessment process it was determined that most streams on the Idaho 1998 §303(d) list in the Upper Owyhee Watershed have cold water aquatic life and salmonid spawning as existing uses. In some cases, data show these uses are not supported due to exceedances of the state of Idaho water quality standards temperature criteria. In other cases, biological information showed impairment to cold water aquatic life and salmonid spawning.

Two streams were listed as not supporting primary and secondary contact recreation due to the presence of bacteria. However, monitoring has indicated those streams are in full support of the recreation beneficial uses.

A TMDL has been developed for each stream determined to be not fully supporting beneficial uses in accordance with state of Idaho water quality standards. The TMDLs address temperature reductions required to meet state of Idaho water quality standard criteria and/or in-stream sediment goals to maintain or restore cold water aquatic life and salmonid spawning. The TMDLs use management objectives dealing with riparian conditions to obtain these goals.

Streams and Pollutants for Which TMDLs Were Developed

Deep Creek: Sediment, temperature
Pole Creek: Temperature
Castle Creek: Sediment, temperature
Red Canyon Creek: Temperature
Nickel Creek: Sediment
Blue Creek Reservoir: Sediment
Juniper Basin Reservoir: Sediment

Subbasin Documents

Upper Owyhee Watershed Subbasin Assessment and Total Maximum Daily Load Owyhee County, Idaho (January 2003)
Upper Owyhee Watershed TMDL Implementation Plan for Agriculture (October 2004)
Upper Owyhee River TMDL Five-Year Review (June 2009)

Department of
Environmental Quality

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