LA FERIA, Texas (Border Report) — An invasive water plant is spreading across the Rio Grande from Mexico to the United States, clogging U.S. canals that supply water to South Texas towns.

It’s called water hyacinth, which originated in aquariums in South America. Somehow, it spread to North America and to South Texas decades ago, but water officials in the Rio Grande Valley say recently it has made a strong comeback and is cause for concern.

The subtropical lily-like pads and purple blooms of what formally is called Pontederia crassipes float atop the water and multiply at a high rate. The hardy plants are hard to kill and are threatening water supplies in the Rio Grande Valley, Border Report has learned.

The Rio Grande appears green but is really covered with South America water hyacinth, says environmentalist Jim Chapman on Tuesday during a tour of the international river that is covered in the invasive plant from shore to shore in some parts of Cameron County, Texas. (Sandra Sanchez/Border Report)

“Water hyacinth is actually an escaped aquarium plant and it thrives in the river and as you can see it is completely clogging the river,” environmentalist Jim Chapman, vice president of the nonprofit Friends of the Wildlife Corridor told Border Report during a trek along the banks of the Rio Grande in rural Cameron County earlier this week.

“It’s a big problem for cities and irrigators who are trying to pump water out of the river because it can clog their intake,” Chapman said.

A water pump is surrounded by carrizo cane, another invasive plant, as it tries to extract water from the Rio Grande near an area covered with South America water hyacinth south of the small town of La Feria, Texas, in rural Cameron County. (Sandra Sanchez/Border Report)

Othal Brand Jr., manager of the Hidalgo County Water Improvement District 3, says the problem is worse in the Lower Rio Grande Valley. In Hidalgo County, in the Upper Valley, he says they are controlling the plant from spreading by putting carp in the Rio Grande.

The fish eat the plants and they have been able to control the spread in the river, but he says workers still must manually clean out pipes where the plants tend to clog intake leading to canals that supply water to farmers, ranchers and residents.

“All of us have a problem wherever we have an open canal,” Brand said.

The main water canal to Harlingen, Texas, appears blocked by water plants on Jan. 25, 2023. U.S. Customs and Border Protection hire contractors to clean out the canal sometimes twice a week due to the hardy invasive plants. (Sandra Sanchez/Border Report)

In Cameron County, closer to the Gulf of Mexico, the river water appears green from a distance as the moss-like hyacinth has completely covered the river in several places.

“The water hyacinth is presenting a problem throughout the Rio Grande River,” Rod Kise, a public affairs officer for U.S. Customs and Border Protection, told Border Report in an email response to several questions. “The water hyacinth is believed to be causing a water supply concern throughout the RGV.”

It’s particularly a problem in Cameron County just west of the tiny town of Los Indios, Texas, where the water hyacinth has invaded the main canal that supplies water to the town of Harlingen.

That’s also near where Texas Gov. Greg Abbott is having crews build 1.5 miles of a state-funded border wall.

Kise said contractors are hired by CBP to clean out an area where border wall grates cross over this canal to connect the federal border barrier structure. Sometimes they have to clean it twice a week to prevent the accumulation of the hyacinth, as well as alligator weed — Alternanthera philoxeroides — which also originated in South America.

“The barriers over the canal are grates,” Kise wrote. “CBP is responsible for having them cleaned.”

The grates remain down to prevent migrants from swimming up the canals if they cross illegally from Mexico, he said.

“The grates are closed to keep them from being exploited by smuggling organizations as is common when there are gates or grates in border infrastructure,” Kise wrote.

Tom McLemore, general manager of the Harlingen Irrigation District, told Border Report that the grates are usually down to keep people from swimming up the canal.

Because the plants live on top of the water, McLemore says, there is still plenty of water flowing below in the canal and they are getting enough water to the border city’s 70,000 residents.

“It does not restrict our flow. We have the ability to move those gates so we can clean them,” McLemore said.

But Brand says the plants have long been a problem for water suppliers in the Rio Grande Valley, going back two decades.

“I put double grills in front of my channel and intake,” he said. “We are blessed. We aren’t having any problems in the river. But when it gets in the channel and canal then it goes berserk.”

Alligator weeds mixed with some water hyacinth are seen in the main canal supplying water to the City of Harlingen in South Texas on Jan. 31, 2023. (Sandra Sanchez/Border Report)

Methods for killing the plant can include spraying chemicals, but water authorities won’t do that if the water is used for drinking.

The Rio Grande supplies drinking water to an estimated 6 million people in two nations, according to the International Boundary and Water Commission, the agency that oversees the river.

Bugs also can be released to destroy the plants, but Chapman says nothing has really been very effective.

“Water hyacinth has been a huge problem for a long, long time,” he said.

And because it floats, and is not attached to the bottom, when one area is free of the pesky plant, it can just travel upstream to another area and spread out.

“It’s on top of the water. It floats. It’s not attached. So you have these floating giant rafts of multiplying hyacinths. It’s actually a very pretty plant with purple blooms,” Chapman said. “But it’s a huge problem.”

“It’s connecting Mexico to the U.S. You can’t walk across it though. That’s for sure,” he said.