National Water-Quality Assessment Project in Texas - Surface Water Activities

Science Center Objects

The USGS National Water-Quality Assessment (NAWQA) Project was established by Congress in 1992 to answer the following question:

What is the status of the Nation’s water quality and is it getting better or worse?

Since 1992, NAWQA has been a primary source of nationally consistent data and information on the quality of the Nation’s streams and groundwater. Data and information obtained from objective and nationally consistent water-quality monitoring and modeling activities provide answers to where, when, and why the Nation’s water quality is degraded and what can be done to improve and protect it for human and ecosystem needs. For NAWQA’s third decade (2013–23), a new strategic Science Plan has been developed that describes a strategy for building upon and enhancing the USGS’s ongoing assessment of the Nation’s freshwater quality and aquatic ecosystems.

At the Texas Water Science Center (TXWSC), NAWQA activities focus on two main areas: surface water and groundwater.


NAWQA will characterize the status and trends of surface-water quality and aquatic ecosystems by monitoring ambient water-quality and ecological conditions through a National Fixed Site Network (NFSN). NFSN data, as well as data collected by State and other agencies, including various agencies in Texas, support the development and refinement of USGS regional water-quality models such as ones that can be used to estimate nutrient loads in Texas’ river systems delivered to the Gulf of Mexico by Texas’ rivers and streams.

Five NFSN monitoring sites are planned for Texas:

  • three large river sites (Brazos, Rio Grande, and Trinity Rivers), and
  • two wadeable streams,
    • one draining a small watershed that is minimally disturbed by development (Frio River) and
    • one that drains the heavily urbanized Dallas metropolitan area (White Rock Creek).

Each of these sites will be sampled between 6 and 24 times per year, every year for

  • basic water-quality properties (pH, conductance, dissolved oxygen, and temperature),
  • major ions,
  • nutrients,
  • organic carbon, and
  • suspended sediment, and
  • at four of the five sites, a comprehensive suite of pesticides and their breakdown products.

At the two wadeable stream sites, ecological sampling of algal, macroinvertebrate, and fish communities will be sampled annually.

Table of Texas NAWQA surface water sampling sites

Texas streams and rivers selected for monitoring by NAWQA, 2013-2023.