The Arroyo Colorado at its historical core is an ancient channel of the Rio Grande that formed during one of the main river’s many flood events.

The Arroyo is 90-miles long. Its headwaters are located south of Mission. From there it winds east – most prominently through Harlingen – in crossing through three counties before flowing into the Laguna Madre. The Arroyo cuts through the heart of the Rio Grande Valley, but its importance as a flood control channel and environmental green belt is largely overlooked.

Samantha Colunga is the Arroyo Colorado Watershed coordinator. She has the challenging role of educating the general public and stakeholders like cities and irrigation districts about the waterway’s vital importance. Improving the Arroyo’s poor water quality is always the big picture goal. There are over 200,000 acres of cultivated farmland along the Arroyo. Runoff of pesticides and other pollutants from those areas is a leading contributor to the containments found in the river channel.

Improvements and efforts are ongoing to make the Arroyo cleaner and to reintroduce native greenery along the banks of the Rio Grande’s offshoot. Colunga is tasked with leading efforts to establish partnerships with the Arroyo’s stakeholders while informing the public about the vital role the river channel plays in Valley life and its bloodstream.

“A lot of people don’t know much about the Arroyo Colorado,” Colunga said. “That’s the challenge. We work to find ways where people can relate to it in the things they care about.”

Getting Public Involved

A recent reforestation event south of Pharr is an example of gaining public interest in bringing back green space along wildlife corridors like the Arroyo.

Historically, the watershed coordinator’s office has worked to establish workshops and community events to encourage protection of water resources and to provide guidance on how to safely dispose of surplus agricultural pesticides. Colunga is a program specialist with the Texas Water Resources Institute and is based in Weslaco at the Texas A&M AgriLife Research and Extension center.

The Arroyo’s watershed areas go far behind where the old river channel flows given the vast amount of RGV area that has runoff going into it. Over 700 square miles consisting of 450,000-plus acres makes up the Arroyo’s watershed. In ancient times, it was a coastal stream of grace and beauty with moss-draped hardwoods and woody vines. Today, its main use is to act as a floodway and conduit used for wastewater conveyance. Runoff from area cities, farms and ranches goes to common points, and a major gathering place for all of that is the Arroyo.

Colunga is an advocate for cities developing more green space in their growing urbanization clusters. She highlights what cities like Harlingen are doing in mandating that at least 15 percent of new developments have green infrastructure. Colunga praised the city of San Benito for turning old waste water ponds into riparian areas with more plant life and healthier soils.

“Plants and trees that are deep rooted act as natural filters,” she said. “All of that green infrastructure will ultimately improve the water quality of the Arroyo.”

Still Playing Important Role

The Arroyo from a natural environmental standpoint isn’t what it was but still plays a vital role in the Valley’s flora and fauna.

It is the primary source of freshwater to the Laguna Madre. The lower 25 miles of the Arroyo act as an important estuary and nursery for many fish and shrimp species. The meandering river channel still has remnants of sub-tropical woodland communities as anyone walking on Harlingen’s arroyo trails can attest to after a long hike. Green jays, kiskadees, herons and chachalacas hopping from tree to tree are common sights in the woodlands and brush along the arroyo.

In its own way, the Arroyo remains a jewel of the Valley. Experts and leaders like Colunga are working to “get everyone together to see what their resources are” in preserving and improving the ancient but still relevant waterway.