Salmon River (South Fork) Subbasin

This document addresses 14 named streams comprising 28 assessment units in the South Fork Salmon River subbasin that were recommended for listing for temperature in the 1991 South Fork Salmon River TMDL. This document addresses the temperature TMDLs for these streams. This document also revises the sediment targets from the 1991 TMDL. Effective shade targets were established for 28 assessment units based on the concept of maximum shading under potential natural vegetation resulting in natural background temperature levels. TMDLs were established for 27 assessment units. Shade targets were derived from effective shade curves developed for similar vegetation types in Idaho. Existing shade was determined from aerial photo interpretation field verified with Solar Pathfinder data. With the exception of Trail Creek and perhaps Profile Creek, all other streams in the analysis lack shade resulting in excess solar load. Many streams were further impacted by recent wildfire. Tributary streams in the Warm Lake area (Warm Lake Creek, Rice Creek, and Trout Creek) have been most affected, resulting in high excess solar loads. Elk Creek in the lower South Fork Salmon River area and Grouse Creek in the Secesh River watershed also appeared to have been affected. Some tributary streams were not as affected and have moderate levels of shade loss and excess solar loading. The lower canyon sections of the major rivers, the South Fork Salmon and Johnson Creek, are in relatively good condition with respect to shade primarily because they are wide with low shade targets to begin with and are in a more sparsely vegetated dry forest zone. Meadow areas were similarly less impacted because of their lower shade targets. In addition to developing temperature TMDLs, this TMDL addendum also revised sediment targets used in the South Fork Salmon River TMDL to more closely reflect natural conditions in the watershed. These targets are based on the Payette and Boise National Forest Watershed Condition Indicators for the watershed.