The federal Clean Water Act requires that states and tribes restore and maintain the chemical, physical, and biological integrity of the nation's waters. States and tribes must adopt water quality standards necessary to protect fish, shellfish, and wildlife while providing for recreation in and on the waters whenever possible.

Section 303(d) of the Clean Water Act establishes requirements for states and tribes to identify and prioritize water bodies that are water quality limited (i.e., water bodies that do not meet water quality standards). States and tribes must periodically publish a priority list of impaired waters, currently every two years. For waters identified on this list, states and tribes must develop water quality improvement plans known as total maximum daily loads (TMDLs) that establish allowable pollutant loads set at levels to achieve water quality standards.

This document addresses the water bodies in the South Fork Boise River subbasin that were placed on Idaho’s 2002 §303(d) list as well as the changes made in the draft 2008 Integrated Report. The subbasin assessment (SBA) describes the physical, biological, and cultural setting, water quality status, pollutant sources, and recent pollution control actions in the South Fork Boise River Subbasin. The TMDL quantifies pollutant sources and allocates responsibility for load reductions needed to return listed waters to a condition of meeting water quality standards. In addition, because the South Fork Boise River subbasin was scheduled for review in 2008. the document also includes a five-year review.

The South Fork Boise River Subbasin is located in southwestern Idaho, east of Boise and predominantly in Elmore and Camas counties. The watershed includes the South Fork Boise River upstream of the slack water of Arrowrock Reservoir, Anderson Ranch Reservoir, and all South Fork Boise River tributaries upstream to the headwaters. The subbasin area is primarily federally owned and administered. Prairie, Pine, and Featherville are the only recognized communities in the watershed that have year-round residents; second/summer/recreational homes are found in numerous sub-divided areas throughout the watershed. Access is provided by many miles of U.S. Forest Service-maintained roads and by county-owned or -maintained roads.

The subbasin consists of 34 separate water body assessment units (previously identified as stream segments. Of these, 14 were identified as water quality limited and were placed on the 2002 §303(d) list. Of these, 5 (listed below) are identified in the subbasin assessment as needing water quality improvement plans known as Total Maximum Daily Loads (TMDLs) to address temperature. Temperature is a water quality factor integral to the life cycle of fish and other aquatic species. Elevated stream temperatures can be harmful to fish at all life stages. Sources of elevated temperature are anthropogenic alterations related to roads, farming, grazing, mining, timber harvest, community or domestic development, or other activities, that reduced stream shade or altered the stream in a way that resulted in increased stream temperatures.

In addition, the subbasin assessment identifies several streams to be added to the state's list of impaired waterbodies for flow and habitat alteration in the next Integrated Report and others to be removed for sediment and unknown pollutants.