Water Quality > Assessment/TMDLs

Water Quality Assessment (303[d]) & Water Quality Improvement Projects (TMDLs)

Water Quality Assessment (303[d])

Washington State's Water Quality Assessment lists the water quality status for a particular location in one of 5 categories recommended by EPA. The assessment represents the Integrated Report for Sections 303(d) and 305(b) of the Clean Water Act.

General 303(d) List Information | Current Assessment | Proposed Freshwater Assessment | more

Water Quality Improvement Projects (TMDLs)

Water Quality Improvement Projects, or TMDLs (Total Maximum Daily Loads) determine the amounts of pollutant loading that a given water body (river, marine water, wetland, stream, or lake) can receive and still meet water quality standards.  Where water bodies do not meet water quality standards for a particular pollutant, TMDLs are implemented through Waste Load Allocations, inserted as pollutant limits in permits to point source dischargers, and through Load Allocations and non-regulatory programs for nonpoint sources, to bring water quality up to standards.

TMDLs Home Page | TMDLs in Your Watershed

Data Quality Assurance

Information on water quality data assurance - what it is, why it is important, and what the State of Washington is doing to support quality assurance of water quality data.

General Data Quality Information | Data Quality Policies