TCEQ Assessment Units

Date(s): Coverage Availability/Geographic Extent: Footprint: Source(s):
Creation date varies Texas State TCEQ

Data Access

Direct Download

The full TCEQ Assessment Units data set can be downloaded directly.

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Data Details

Available Formats: Shapefile, Geo-Database, KML
Alternative Data: None
Derivative Data: None
Known Issues: None
Recommended Uses: Basemap, Research, Analysis
Spatial Reference:

EPSG 4269


This layer depicts the official TCEQ Segments at the Assessment Unit (AU) level for the State of Texas as listed in Title 30, Chapter 307 of the Texas Administrative Code (TAC), also known as the Surface Water Quality Standards. These are streams and waterbodies that have been individually defined by the TCEQ and assigned unique identification numbers. Intended to have relatively homogeneous chemical, physical, and hydrological characteristics, a segment provides a basic unit for assigning site-specific standards and for applying water quality management programs of the agency. Both "classified" and "unclassified" segments have been included in this layer. Classified segments, also referred to as designated segments, refer to water bodies that are protected by site- specific criteria. The classified segments are listed and described in Appendix A and C of Chapter 307.10. The site-specific uses and criteria are described in Appendix A. Classified waters include most rivers and their major tributaries, major reservoirs, and estuaries. Unclassified waters are those smaller water bodies that do not have site-specific water quality standards assigned to them, but instead are protected by general standards that apply to all surface waters in the state. This layer also indentifies which assessment units have been assessed in the DRAFT 2010 Texas Integrated Report for Clean Water Act Sections 305 (b) and 303 (d). An impaired assessment unit is a water body included in Category 5. Water bodies in Category 5 do not meet applicable water quality standards or are threatened for one or more designated uses by one or more pollutants.

General purpose use; to support agency-wide policy decisions regarding surface water quality in the State of Texas. Due to the various scales inherent from using multiple sources in the creation of this dataset, this layer should not be used for making important decisions at scales greater than 1:250,000.