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 is a subbasin assessment only. It describes the physical, biological, and cultural setting; water quality status; pollutant sources; and recent pollution control actions in the Lochsa River Subbasin.

The Lochsa River Subbasin encompasses predominately undeveloped forest land and free flowing streams. Most of the Lochsa River itself is designated as a Wild and Scenic River and approximately half of the subbasin lies in the Selway Bitterroot Wilderness Area. The streams in the subbasin are home to a variety of fish, including Chinook salmon, steelhead, mountain whitefish, and bull trout.

Twenty-five tributary stream segments were §303(d) listed for sediment. Available data show that the sediment concentrations in the streams are within the normal range that is expected in the subbasin. Data also show that all 25 listed tributary stream segments support their beneficial uses. DEQ recommends all the segments be delisted for sediment.

The Lochsa River and one tributary stream segment were §303(d) listed for temperature. DEQ reviewed habitat, fish, and temperature data and concluded that, while water temperatures do exceed the state's criteria during parts of the year, these exceedances are natural and the river and its tributaries support their designated uses. DEQ recommends that the Lochsa River and the one tributary listed for temperature be removed from the §303(d) list for temperature.

As all listed stream segments were recommended for delisting, no TMDLs were developed.