Desert Evening at Big Bend, by Louis Vest
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Ecologically Unique Rivers


This dataset was created to show river and stream segments that provide ecological value to Texas’ wildlife species and ecosystems.

Data Layer Description


Texas Parks and Wildlife Department (TPWD)




Ecologically Unique River and Stream Segment data (31 TAC 357.8) was updated in August of 2008 using flowlines from National Hydrography Dataset (NHD) Plus. These segments are “protected” according to the Texas Water Code Section 16.051. The Texas legislature can officially designate stream segments as being of unique ecological value following nomination of stream segment by a regional planning group. By so doing, a state agency or political subdivision may not obtain a fee title or an easement that would destroy the unique ecological value of a designated stream. It should be noted that these stream segments do not have to correspond to classified water quality segments. This dataset was created by Albert El-Hage (TPWD) in 2002 and updated by Lynne Hamlin (GISP Water Resources Branch of TPWD) in 2008. As a result of the passage of Senate Bill 1 in 1997, water planning in Texas became the domain of regional planning groups rather than the Texas Water Development Board (TWDB).  As a part of the planning process, each regional planning group may include recommendations for the designation of ecologically unique river and stream segments in their adopted regional water plan.  Stream segment designation is to be supported by a recommendation package that includes a physical description, maps, photographs, literature citations, and data pertaining to each candidate stream segment.  In accordance with the TWDB’s rules, the following criteria are to be used when recommending a river or stream segment as being of unique ecological value:

    • Biological Function: Segments which display significant overall habitat value including both quantity and quality considering the degree of biodiversity, age, and uniqueness observed and including terrestrial, wetland, aquatic, or estuarine habitats;
    • Hydrologic Function: Segments which are fringed by habitats that perform valuable hydrologic functions relating to water quality, flood attenuation, flow stabilization, or groundwater recharge and discharge;
    • Riparian Conservation Areas: Segments which are fringed by significant areas in public ownership including state and federal refuges, wildlife management areas, preserves, parks, mitigation areas, or other areas held by governmental organizations for conservation purposes under a governmentally approved conservation plan;
    • High Water Quality/Exceptional Aquatic Life/High Aesthetic Value: Segments and spring resources that are significant due to unique or critical habitats and exceptional aquatic life uses dependent on or associated with high water quality; or
    • Threatened or Endangered Species/Unique Communities: Sites along segments where water development projects would have significant detrimental effects on state or federally listed threatened and endangered species, and sites along segments that are significant due to the presence of unique, exemplary, or unusually extensive natural communities.

How to get the data layer

Contact the TPWD GIS Lab Manager, Kim Ludeke.

How you might make use of this data layer

Ecologically Significant Stream Segment data are an important conservation layer that has the potential to be identified in Regional Water Plans throughout Texas, identify important riparian areas for Texas’ wildlife and ecoregions, and recognize river segments with valuable hydrological and biological functions.

How to get more information

For a detailed description of the dataset view the Ecologically Significant Stream Segment website.  NHD Plus data is available from their website

Access and use constraints

Attribution Non-Commercial (BY-NC) - This license lets others remix, tweak, and build upon our work non-commercially, and although their new works must also acknowledge us and be non-commercial, they do not have to license their derivative works on the same terms. (http://creativecommons.Org/licenses/by-nc/3.0/)


Texas Parks and Wildlife Department (TPWD). August 2008.

Sample Map

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