Note: This is the first in a series about the groundwater in the Borderland. The second edition, which examines groundwater solutions, will be published later this month.
Sluggish waters flow and pool beneath the Borderland, providing water to millions of people in Far West Texas, northern Mexico, and southern New Mexico.
From Las Cruces to Ciudad Juárez to El Paso, cities rely on pumping water out of the ground to survive. Despite efforts to conserve groundwater, cities are pumping faster than aquifers are renewing.
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Climate change is drying up the Rio Grande, making the river a less reliable source of water for the region. This has resulted in the region’s urban users and farmers alike having to rely on the region’s groundwater as a fallback option when the river cannot deliver.
The region’s common aquifers are also facing growing populations and decades of overuse. Water experts said border communities need to work together to protect aquifers from overexploitation and pollution – a prospect made difficult by the border’s surroundings.
Groundwater is complicated – difficult to describe, difficult to measure, and water quality varies across the region.
“Unlike surface water, where we can see floods or droughts, groundwater is invisible,” said Sharon B. Megdal, director of the Water Research Center at the University of Arizona. “Many of the border communities are dependent on this pumped water.”
The surface water is managed through treaties, but there is currently no formal groundwater management agreement between the United States and Mexico for its common aquifers, Megdal said.
“It’s a difficult puzzle. But if we don’t do anything, the communities run the risk of overexploiting their water resources (and) that extraction becomes much more expensive because you go deeper or the quality changes, ”Megdal said.
Geology, hydrology and wells
In past geological times, rivers or lakes could penetrate rock formations through the shifting of tectonic plates under the earth’s crust. These “fossil” rivers are eventually covered by land and form the basis of the Hueco and Mesilla Bolsons, which are found under Texas, New Mexico, and Chihuahua. These underground pools are recharged by rain pouring down from the mountains.
The geological formations that make up the aquifers stretch for miles, across counties, states, and the border.
The Hueco Bolson is about 200 miles long and 25 miles wide below Texas and in Chihuahua; it has a maximum thickness of 9,000 feet deep. Only the upper several hundred feet have fresh water, while much of the other water is brackish or slightly salty, and the lower parts are extremely salty.
The Mesilla Bolson has a maximum thickness of 2,000 feet, extends under New Mexico and Chihuahua for a length of 62 miles and a width of 6.4 miles. Little water flows between the two Bolsones and they are considered to be separate systems.
The rocks gradually flood as water is released into the Rio Grande from the Caballo Dam in New Mexico. Mountains and river beds form watersheds that recharge and restore aquifers. (Corrie Boudreaux / El Paso Matters)
The arid, arid desert climate slows the recharge process to about 33,000 acre-feet of water, or about 10 billion gallons per year from various sources, including mountains, the Rio Grande Canal, or unlined canals.
Zhuping Sheng, a researcher with the Texas Tech AgriLife Transboundary Aquifer Assessment Program, said access to this water means drilling wells in El Paso to a depth of approximately 75 meters.
“Think of a sponge, the water stays in the holes,” said Sheng. “When you pump, it basically pushes water out of this point.”
Sheng said the easiest way to think of the aquifer is like a savings account for a bank, with withdrawals from pumping and deposits from injections and natural recharging.
“We keep using it – faster in dry years, more when there’s less river water – but we’re moving on,” Sheng said.
The biggest pump
Robert Mace, executive director of the Meadows Center for Water in the Environment at Texas State University, said Texas groundwater law follows an older English concept called the trapping rule.
“If I get the groundwater first before you do, there is nothing you can do. Another way to put it is sometimes the ‘Law of the Biggest Pump,’ ”Mace said. “If I put in my well and drain your well, you have no legal recourse.”
Only 10 other states are applying the rule of capture standard and few changes have been made to limit free access to groundwater. Texas allows local water protection districts to enact rules that replace the rule of registration. In general, districts have restrictions on pumping or clearance requirements to minimize the impact of pumping on the land and water of neighbors.
However, El Paso is not managed by a local groundwater protection area.
In 1998, the Texas Legislature ruled that El Paso County was a priority groundwater management area – which means that current or future declines could force it to form a local groundwater regulation group. After a series of reviews, commissioners for the Texas Commission on Environmental Quality’s predecessor, the Texas Natural Resource Conservation Commission, wrote at the time that El Paso “has clearly shown significant efforts in regional collaboration, planning and voluntary implementation.” Addressing water supply problems ”and would not need further supervision from a local district.
Ed Archuleta, who was CEO of El Paso Water at the time, said TCEQ commissioners determined that the utility’s 50-year plan for water management, conservation and conversion to surface water would eliminate the need for another agency.
“In other words, we have already managed the water well,” said Archuleta.
The federal government has traditionally taken its hands off groundwater and left regulation to the states, Mace said.
“Any discussion of trying to include the groundwater component in the international agreement with Mexico is perceived by many as a potential threat to federal regulation or groundwater resources,” Mace said. “There is great resistance at the country and even at the local level.”
The fresh water problem
A 2004 study estimated freshwater in the Texan portion of Hueco Bolson to be 9 million acre-feet, nearly 3 trillion gallons. But even that number fluctuates as high as 20 million acre-feet, depending on the model used to measure capacity.
Alex Mayer, who heads the Center for Environmental Research Management at the University of Texas at El Paso, said the first challenge is measuring the aquifer and called it a “best educated guess” scenario. Modeling requires expensive and extensive drilling and remote sensing to better understand where the water moves underground. He said the water usage measurements are based on systems of self-reported data – be it from a utility like El Paso Water to a farmer’s own estimates of watering crops.
“It’s about the transparency of the data. It is very difficult to quantify a resource if you don’t know how much is there and how much is being removed and at what rate, ”said Mayer.
Water pours into an irrigation canal near Garfield, New Mexico. Elephant Butte and Caballo Reservoirs were opened in late May to provide water for irrigation to southern New Mexico and El Paso. (Corrie Boudreaux / El Paso Matters)
If El Paso and Ciudad Juárez continue in “business-as-usual” manner, Mayer estimates that there will still be 30 to 60 years of freshwater in the aquifer, depending on how “optimistic” the climate models look.
Ciudad Juarez’s requirement requires that 49 billion gallons, or approximately 151,000 acre-feet, be completely pumped out of the two aquifers annually. That simply exceeds the usage of El Paso, even though Juárez has twice the population. Both cities agreed on an informal exchange of data, but no formal agreements on water management.
Utilities El Paso Water split supplies between groundwater and treated river water for an average of about 118,000 acre-feet, or 38 billion gallons, within the city each year. The non-incorporated parts of the El Paso district rely exclusively on groundwater.
About 40% of the city’s water comes from the Hueco Bolson aquifer; it receives another 17% from the renewable Mesilla Bolson Aquifer west of the Franklin Mountains, 5% from the removal of salt from the brine, and the Rio Grande provides the remaining 38%.
El Paso Water pumps 60,000 to 70,000 acre-feet – or between 19 billion and 22 billion gallons – from the Hueco Bolson every year.
Since the 1990s, the utility has worked to reduce demand and put conservation practices in place to conserve groundwater.
The utility uses injection wells to return 3 million gallons of purified wastewater to the aquifer every day. Using a combination of wells and ponds, the utility has put 30 billion gallons back into the ground since the 1990s.
Scott Reinert, El Paso Water’s water resources director, said this stabilized the water table, which had plummeted hundreds of feet in the 1970s and 1980s from pumping too high.
Reinert said the core problem with groundwater depletion is not that the water is running out.
“The cheap water is running out,” he said.
Cover picture: A diesel-powered groundwater pump outside of Fabens. (Danielle Prokop / El Paso Matters)