This dataset depicts TMDL watershed boundaries. A TMDL watershed is the area covered by a TMDL equation. It consists of one or more impaired streams that have an assigned Cause Group Code (CGC). The CGC is the link between the TMDL and the Assessment Report. The TMDL equations are stored in a table in the TMDL database. Currently, the database contains about 650 equations, which are set across the entire state. Each equation includes the Waste Load Allocation (WLA), which is the portion of the TMDL that accounts for pollution from point sources (permits). The WLA cannot be exceeded during permit reissuance or its TMDL equation must be modified.

Polygon layer representing all watershed Boundaries for the Implementation Watersheds, including Approved, In Progress and Completed Implementation Areas.