Description:

Importance of Clean Water Act Section 303(d) Listing Information Section 303(d) waters show water quality standards impairments or threats to the attainment of beneficial uses or anti-degradation provisions. This map is a representation of threatened and impaired streams, rivers, coastlines, estuaries, lakes and wetlands within an 8 -digit Hydrologic Unit Code (HUC), divided by the total number of water miles within the HUC. Access to Detailed Data Access to detailed data for each data layer is available through "Surf Your Watershed." Data Sufficiency Thresholds All 303(d) listing information available and mapped as of July 1999 was included. Notes on Interpreting this Information Many waterbody types such as estuaries, wetlands and lakes are typically measured in square miles or acres. For the sake of comparison, this analysis measured all of these waterbodies in miles. The impaired and threatened water mileage for lakes and estuaries was calculated using the distance for a line running through the middle of the waterbody. The exceptions to this method include the Great Lakes, Long Island Sound, Delaware Bay, and Chesapeake Bay. For these waters their coastline mileage was used. Breakpoints for the scores were determined using modified quantiles. Plans to Improve this Layer This layer will be improved as listing data for more watersheds become available. There is also an ongoing effort by EPA to locate additional waterbody listings. The method for calculating both the total number of water miles within a cataloging unit and the total impaired mileage may be revised after additional review.

URLs/Downloads:

IV22_R3MAP_1.GIF

IV22_R6MAP_1.GIF

IV22_USSCR_1.TXT

IV22_R9MAP_1.GIF

IV22_R4MAP_1.GIF

IV22_R2MAP_1.GIF

IV22_R1MAP_1.GIF

IV22_R8MAP_1.GIF

IV22_R10MAP_1.GIF

IV22_FS_1.WPD

IV22_USFLW_1.GIF

IV22_R5MAP_1.GIF

IV22_USMAP_1.GIF

IV22_USSTB_1.TXT

IV22_R7MAP_1.GIF

Record Details:

Record Type:DATA SET

Product Published Date:08/06/1999

Record Last Revised:11/20/2003

Record ID: 10236