Department of
Environmental Quality

Subbasin at a Glance

Overview

The Boise-Mores Creek Watershed Subbasin is located in southwest Idaho, about seven miles east of Boise, Idaho, predominantly in Boise County with small parts in Ada County and Elmore County. The subbasin includes Mores Creek, Grimes Creek, and all tributaries upstream to the headwaters as well as Lucky Peak and Arrowrock Reservoirs and the Middle Fork Boise River to the confluence of the North Fork Boise River. Of the 400,000 acres in the watershed, 81.5 percent are forest and 17.4 percent rangeland. Idaho City and Placerville are the only recognized cities in the watershed. Other incorporated cites in Boise County include Horseshoe Bend, Crouch, Garden Valley, and Lowman.

TMDLs were developed for the two §303(d)-listed streams (Mores and Grimes Creeks). A sediment TMDL has been developed for all segments of Mores Creek and two segments of Grimes Creek. Another TDML addresses temperature impairment of Mores Creek and thermal contributions of its tributaries including Smith Creek, Thorn Creek, Elk Creek, Grimes Creek, Granite Creek, Macks Creek, Daggett Creek, and Robie Creek. Part of the Boise River is recommended to be added to the §303(d) list due to temperature impairment.

No TMDLs were completed for habitat alteration or flow alteration in accordance with DEQ and EPA policy. DEQ proposes listing certain segments of Mores Creek, Elk Creek, Grimes Creek, and Granite Creek in the next Integrated Report for habitat alteration and flow alteration, however, due to impacts from historic placer mining.

Streams and Pollutants for Which TMDLs Were Developed

Mores Creek

Temperature, sediment

Smith Creek

Temperature

Thorn Creek

Temperature

Elk Creek

Temperature

Grimes Creek

Temperature, sediment

Macks Creek

Temperature

Daggett Creek

Temperature

Robie Creek

Temperature

Subbasin Document

• Boise-Mores Creek Watershed Subbasin Assessment and Total Maximum Daily Loads (June 2009)