EPA Office of Water (OW): 303(d) Listed Impaired Waters, Arizona (streams)

The 303(d) Listed Impaired Waters program system provides impaired water data and impaired water features reflecting river segments, lakes, and estuaries designated under Section 303(d) of the Clean Water Act. Each State will establish Total Maximum Daily Loads (TMDLs) for these waters. Note the CWA Section 303(d) list of impaired waters does not represent waters that are impaired but have an EPA-approved TMDL established, impaired waters for which other pollution control mechanisms are in place and expected to attain water quality standards, or waters impaired as a result of pollution and is not caused by a pollutant; therefore, the "Impaired Waters" layers do not represent all impaired waters reported in a state's Integrated Report, but only the waters comprised of a state's approved 303(d) list. For more information regarding impaired waters refer to EPA's Integrated Reporting Guidance at: http://www.epa.gov/owow/tmdl/guidance.html 303(d) Waterbodies are coded onto NHD linear and area features to create Linear, Polygonal and Point Events. Point events represent impaired waterbody segments that do not fall on an NHD reach. 303(d) Waterbodies are coded onto NHD Waterbody reaches (region.rch) to create datasets. In addition to NHD reach indexed data there may also be custom event data (point, line, or polygon) that are not associated with NHD and are in an EPA standard format that is compatible with EPA's Reach Address Database. These custom features are used to represent locations of 303(d) waterbodies that are not represented well in NHD.