Skip to Content
Questions or Comments:

Arroyo Colorado: Watershed Protection Plan

This is a completed planning and assessment project to improve water quality in the Arroyo Colorado.

aerial photo of Arroyo Colorado and Laguna Atascosa
Laguna Atascosa
near the mouth of the Arroyo Colorado
map of the Arroyo Colorado watershed

Counties: Cameron, Hidalgo, Willacy
Parameter: Dissolved oxygen
Basin: Nueces–Rio Grande Coastal Basin
Segment: 2201

On this page:

Background and Goals

The state of Texas requires that water quality in the Arroyo Colorado be suitable for swimming, fishing, and a healthy aquatic ecosystem. However, dissolved oxygen levels are sometimes too low downstream of the Port of Harlingen (Segment 2201) to provide optimum conditions for fish and other aquatic life.

Oxygen gas, which dissolves in water, is essential for the survival of aquatic life. While the amount of dissolved oxygen in water fluctuates naturally, various human activities can cause unusually or chronically low dissolved oxygen levels which may harm fish and other aquatic organisms.

In July 2002, the TCEQ initiated a project with area stakeholders to develop a watershed protection plan (WPP). Results of a total maximum daily load (TMDL) analysis developed in 2002 by the TCEQ indicated that the dissolved oxygen problem in the tidal segment was related as much to the physical setting and geomorphology of the Arroyo Colorado as it was to the loading of nutrients and oxygen-demanding substances from the non-tidal segment.

TCEQ’s TMDL program facilitated local efforts to develop a watershed protection plan (WPP) to improve water quality conditions in the Arroyo Colorado. Working with the TCEQ and other agencies, the Arroyo Colorado Watershed Partnership, a group of local stakeholders and interested parties, developed A Watershed Protection Plan for the Arroyo Colorado–Phase I.

The Phase I Arroyo WPP describes the measures proposed for implementation from 2007 through 2017 to improve water quality and habitat in the Arroyo Colorado. The stakeholders published an update to the WPP in August 2017.

Description of Watershed

The Arroyo Colorado, an ancient distributary channel of the Rio Grande, extends about 90 miles from Mission, Texas to the Laguna Madre in the Lower Rio Grande Valley. Flow in the Arroyo Colorado is sustained by wastewater discharges, agricultural irrigation return flows, urban runoff, and base flows from shallow groundwater. Although an integral part of a major floodway system, water is rarely directly diverted from the Rio Grande into the Arroyo Colorado (direct diversions occur only during major flood events). The Arroyo Colorado is also the major source of fresh water to the lower Laguna Madre, an economically and ecologically important resource to the region.

The Arroyo Colorado watershed includes 706 square miles of flat coastal plain that slopes gently toward the Gulf of Mexico. The fertile farmland, long growing season, and access to water from the Rio Grande for irrigation make this region one of the most productive agricultural areas in the U.S. The Laguna Atascosa National Wildlife Refuge and several county and city parks are located within the Arroyo Colorado watershed. The mild climate, semi-tropical plants and animals, and many recreational opportunities draw large numbers of people to the Arroyo Colorado watershed. One third of the stream also is used for shipping from the Gulf Intracoastal Waterway to the Port of Harlingen.

Learn more about water quality standards, monitoring, and TMDLs by reading Preserving and Improving Water Quality, available on our website or in print.

Public Participation

A steering committee, which is no longer active, was established to advise TCEQ on the original project to develop a TMDL for dissolved oxygen. The steering committee established five work groups to address key elements of the TMDL. The steering committee included representatives from permitted wastewater dischargers, agricultural groups, universities, citizen groups, and local, state, regional, and federal government agencies.

To develop the watershed protection plan, stakeholders in the area then established the independent Arroyo Colorado Watershed Partnership (ACWP) . The ACWP, in cooperation with the TCEQ, established several work groups to address the seven major components of the watershed plan. These workgroups submitted their recommendations to the Partnership’s steering committee in 2006. The recommendations were incorporated into the final WPP document, which was published in January 2007. A copy of the Arroyo WPP is available at .

Watershed Plans

The original Watershed Protection Plan was developed by the region's stakeholders in partnership with several state and federal agencies.

In 2017, stakeholders in the area updated their plan. See it on the website of the Arroyo Colorado Watershed Partnership .

The Pollutant Reduction Plan describes the regulatory and voluntary measures in effect from 2006 through 2015 to reduce the pollutant loadings from sanitary wastewater flowing into the Arroyo Colorado.

The TCEQ Nonpoint Source Program and the EPA are providing support for implementing the WPP.

Contact the TMDL Program

Please email and mention the Arroyo Colorado in the subject line. Or call us at 512-239-6682.

Back to the top of the page Back to top

Communities Working Together: TCEQ TMDL Program Long Logo