The Arroyo Colorado flows through Hidalgo, Cameron and Willacy Counties in the Lower Rio Grande Valley of Texas into the Laguna Madre (Figure 1). As a result of low dissolved oxygen levels, the tidal segment of the Arroyo Colorado (2201), does not currently meet the aquatic life use designated by the State of Texas and described in the Water Quality Standards. This has been the case for every 303(d) list prepared by the state since 1996. There have also been concerns for high nutrient levels in this river as documented on every 305(b) assessment prepared by the state since 1998. In order to meet the dissolved oxygen criteria (24-hour average of 4.0 mg/L and minimum of 3.0 mg/L) at least 90% of the time between the critical period of March through October, the Texas Commission on Environmental Quality (TCEQ) (2003) estimates a 90% reduction in nitrogen, phosphorous, oxygen demanding substances and sediment will be necessary.
Watershed Protection Plan (WPP)
In response to this impairment, a local effort was initiated to develop a WPP to improve conditions in the Arroyo Colorado. Working with the TCEQ, the Texas State Soil and Water Conservation Board (TSSWCB), and other agencies, a local steering committee has devised and begun to implement strategies to increase dissolved oxygen in the Arroyo and improve its environmental condition.
The consensus-based, local effort began in July 2003 with the formation of the Arroyo Colorado Watershed Partnership. The Arroyo Colorado Watershed Partnership Steering Committee, consisting of local stakeholders and agency representatives, and workgroups provided direction for the Arroyo Colorado Watershed Partnership in development of the Arroyo Colorado WPP. Texas Sea Grant College Program and the AgriLife Extension Service facilitated and coordinated the development of the WPP through funding provided by TCEQ through a Clean Water Act (CWA) Section 319(h) grant. The WPP included five major components: Wastewater Infrastructure; Agricultural Issues; Habitat Restoration; Further Study and Monitoring/ Refinement of TMDL Analysis; and Outreach and Education. The five workgroups developed recommendations for each of their components including action items that will improve water quality. As a result of their efforts, the “Watershed Protection Plan for the Arroyo Colorado, Phase I” was developed and released in 2007.
Implementation of the Arroyo Colorado WPP is a priority for the TECQ Nonpoint Source (NPS) Pollution Program, and this partnership will address and implement a number of Storm Water Management and Education & Outreach elements identified in the plan. As stated in the land use section of the Arroyo Colorado WPP, “The Arroyo Colorado Watershed Partnership seeks to develop, promote and achieve sound land use practices that protect and preserve watershed resources, maintain water quality and minimize pollutants entering the Arroyo Colorado.” One of the goals of the Arroyo Colorado WPP is to increase awareness of and promote development options that incorporate elements of Smart Growth and Low Impact Development (LID). LID is an approach to land development or re-development that works with nature to manage storm water as close to its source as possible. LID employs principles such as preserving and recreating natural landscape features, minimizing effective imperviousness to create functional and appealing site drainage that treats storm water as a resource rather than a waste product. There are many practices that have been used to adhere to these principles such as bioretention facilities, rain gardens, vegetated rooftops, rain harvesting systems, and permeable pavements. By implementing LID principles and practices, water can be managed in a way that reduces the impact of built areas and promotes the natural movement of water within an ecosystem or watershed. Applied on a broad scale, LID can maintain or restore a watershed’s hydrologic and ecological functions. LID has been characterized as a sustainable stormwater practice by the Water Environment Research Foundation and is a key component of the EPA’s national program to address urban NPS pollution. This can be achieved using onsite measures such as vegetated swales, rain gardens, green roofs, porous pavement and larger-scale practices such as retention ponds.
The Lower Rio Grande Valley continues to be one of the fastest-growing areas in the United States. With urbanization ever increasing within the Lower Rio Grande Region, the remaining public lands in this region will face ever increasing pressure to accommodate off site rainwater discharges from encroaching developments, subdivisions and planned communities. Incorporating successful BMPs into facility infrastructures and amenities at the refuge and/or public lands will optimize benefits from on-site rainfall. Likewise, incorporating successful BMPs will improve facility infrastructures and amenities to reduce the negative impact from contaminated off-site runoff.