In South Texas, an old water system meets a region in flux
McALLEN, Texas — On a scorching afternoon in South Texas, Sonia Lambert looked at an open-air canal that carries mud-green water from the Rio Grande to nearby towns and farmland, losing much of it to evaporation and seepage along the way.
“That will be someone else’s problem,” Lambert said, referring to her upcoming retirement as head of an irrigation district near the U.S.-Mexico border.
In the Rio Grande Valley, a canal system designed over 100 years ago for agriculture still delivers water to the region’s lush farmland and fast-growing towns and cities. Today, the canals lose as much as 40% of the water they carry, waste that experts say could contribute to steep water shortages in coming decades as the population grows and climate change intensifies droughts.
“As this region continues to become drier due to climate change, water supplies will be greatly reduced,” said Guy Fipps, a professor of irrigation engineering at Texas A&M University who has studied the water system since 1998.
State water officials predict that over the next 50 years, demand for water in the area’s cities and towns will double.
For decades, McAllen developed at a dizzying pace, with newcomers drawn to a large free-trade zone and jobs in health care, education and retail. Between 1990 and 2020, McAllen and the neighboring cities of Edinburg and Mission grew sixfold to nearly 871,000 people, according to the U.S. Census Bureau. Similarly, the Mexican cities of Reynosa and Matamoros across the border mushroomed after U.S.-owned assembly plants were established in the mid-1990s.
Further complicating matters is a 1944 treaty between the U.S. and Mexico that defines how the countries share water from the Rio Grande. Mexico is supposed to route 350,000 acre-feet of water every year to the U.S. — enough to supply as many as 700,000 households. But it has periodically failed to meet those obligations, delaying deliveries because of drought, tight water supplies and a thirsty crop industry in northern Mexico.
The late deliveries are a source of frustration, but water managers and farmers in the U.S. are quick to acknowledge a major challenge at home too: the leaky canal system that has long been seen by local and state officials as too expensive to overhaul.
The region’s more than 2,000 miles of pipelines and canals — some 100-feet wide — are meant for large, infrequent deliveries to farmland. Common fixes to modernize the waterways and make them more efficient — attempted by many districts to some degree — include lining earthen canals with concrete and more closely monitoring water use by farms with meters. Another option comes with a bigger price tag: replacing canals with underground pipelines, which lose far less water and are better suited to serving cities.
Converting a mile of open-air canal into underground pipelines costs between $250,000 and $1 million, said Lambert, the irrigation district manager for Cameron County, which remains mostly rural. Her district has only been able to bring about a fifth of its 250 miles of canals underground in the past two decades, she said.
Since the early 1900s, a network of about two dozen independent irrigation districts have served the area’s farmers, cities and towns. But as McAllen gobbled up much of the farmland surrounding it, some officials have wanted more control over a water district they say charges the city too much for water deliveries.
Yet the higher rates charged to city water utilities are often how irrigation districts pay for canal repairs, said Fipps. That has meant the water districts serving bigger cities have generally made more progress in bringing canals up to date.
Still, the Rio Grande Valley’s water utilities and farms are linked by the same aging system.
Since cities and farms get water from the same canals, hydrologists and water officials say the Rio Grande’s shrinking flows and low reservoir levels could eventually spell trouble for everyone in a prolonged drought. When there’s little water in a canal, a greater percentage gets lost to evaporation or seepage.