TR-467 Sustainability of the Arroyo Colorado Watershed Partnership and Continued Implementation of the Arroyo Colorado Watershed Protection Plan Final Report

Authors: J. Flores, T.A. Berthold

The Arroyo Colorado (AC) is an ancient channel of the Rio Grande and is approximately 90 miles long. The headwaters of the AC begins at the Anzalduas Diversion Dam in Mission, TX and flows eastward through southern Hidalgo County, into Cameron County until it makes a North-North Easterly turn through the city of Harlingen and Rio Hondo and eventually discharging into the Laguna Madre near the Cameron-Willacy County line. The AC has been impaired for low dissolved oxygen (DO) levels within the tidal segment since 1996. The AC tidal segment does not meet the aquatic life use designated by the State of Texas and described in the Water Quality Standards. Additionally, bacteria has always been a parameter of concern for the AC and as of 2006, both the tidal and non-tidal segments of the AC were listed on the 303d list of impaired water bodies due to elevated levels of bacteria.

The Arroyo Colorado Watershed Protection Plan: Phase I (ACWPP) is a comprehensive watershed-based strategy developed by the Arroyo Colorado Watershed Partnership (ACWP) to address these impairments over a 10-year implantation period. The ACWPP primarily addresses the low DO levels in the tidal segment of the AC. The goal of the ACWPP is to reduce the addition of pollutants such as oxygen-demanding substances, nitrogen, phosphorus and sediment to the AC and to improve natural habitat to the degree necessary to meet the uses designated by the State of Texas. Although not specifically targeted for reduction, fecal bacteria loading to the AC is also expected to diminish as a result of the ACWPP implementation. The ACWPP takes into consideration the current uses of the water body, including flood control, navigation, conveyance of municipal/industrial wastewater discharges and irrigation return flows, recreation, and environmental uses and presents a detailed strategy to restore and protect these uses. The WPP included five major components: Wastewater Infrastructure; Agricultural Issues; Habitat Restoration; Further Study and Monitoring/ Refinement of TMDL Analysis; and O&E. The five workgroups developed recommendations for each of their components including action items that will improve water quality.