Cumulative Impacts

The cumulative impact of multiple pollution sources may exceed the capacity of the aquatic system to assimilate them. Many permitted point source discharges combine with nonpoint source inputs to account for most of the degradation of southern Appalachian aquatic habitats. Furthermore, loadings of all pollutants tend to accumulate downstream. In large watersheds, the cumulative effect of all activities within the watershed from land use and pollution can be considerable.

The most recent regulatory efforts to address the accumulated impacts have been to determine Total Daily Maximum Loads (TMDLs) for a waterway. A TMDL is a calculation of the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards, and an allocation of that amount to the point and nonpoint sources.  Policies that pertain to TMDLs are still being debated and drafted.