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.

The Salmon Falls Creek Subbasin is located in south central Idaho. Water quality in the Salmon Falls Creek Subbasin, in general, is of good to moderate quality. However, Salmon Falls Creek Reservoir is one of the few water bodies in the state with identified mercury contamination. Sediment, nutrients, and temperature are the most common listed pollutants throughout the subbasin.

In most of the listed assessment units, it was determined that total phosphorus was a limiting nutrient. However, in the Big Creek and Cottonwood Creek watersheds it was determined that total phosphorus was in excess and may be impacting the beneficial uses of Shoshone Creek.

While the majority of stream systems appear to have little impact from excess
nutrients, the same cannot be said for the two reservoir systems. Both Cedar Creek and Salmon Falls Creek Reservoirs contain excess nutrients that lead to nuisance aquatic vegetation blooms. TMDLs are proposed for the tributary systems that feed these two reservoirs. Only nonpoint sources and natural soil-associated phosphorus contribute to this increase in total phosphorus concentrations, as there are no
point sources located within the watershed.

In the lower section of Salmon Falls Creek, where ground water plays a significant role in the hydrology of the system, it was determined that nitrogen was in excess and could lead to nuisance aquatic vegetation growths.

It is EPA policy that flow and habitat alterations are pollution and not specific pollutants, and TMDLs are not required. However, streams found to be impacted by these forms of pollution will remain on the §303(d) list. Cedar Creek below the Cedar Creek Reservoir falls into this category for flow alteration.

All streams listed for temperature were examined and require load reductions as a result of lack of shade.

Although not currently listed on the integrated report, Salmon Falls Creek Reservoir was examined due to a fish consumption advisory placed on the water body in 2001. Fish tissues were collected in October 2006. Mercury concentrations found in fish at that time averaged well above DEQ's fish tissue criterion. In order to achieve the water quality standard, mercury levels need to be reduced by nearly 70%.

In addition, DEQ proposes to remove the following water bodies from the
state's list of degraded waters for specific pollutants for which TMDLs have already
been completed:

• Salmon Falls Creek Lower: bacteria and dissolved oxygen
  
• Shoshone Creek: bacteria
  
• Hot Creek: sediment
  
• Cottonwood Creek: dissolved oxygen