A diesel powered groundwater pump outside of Fabens. (Danielle Prokop/El Paso Matters)

Note: This is the first in a series about the groundwater in the Borderland. Read part two here.

Sluggish waters flow and pool beneath the Borderland, offering water for millions of people in Far West Texas, Northern Mexico and Southern New Mexico.

From Las Cruces to Ciudad Juárez to El Paso, the cities rely on pumping that water out of the ground to survive. Despite efforts to conserve groundwater, the cities are pumping faster than the aquifers recharge.

Climate change is drying up the Rio Grande, making the river a less reliable source of water for the region. That’s made the area’s urban users and farmers alike rely on the region’s groundwater as a fallback option when the river can’t provide.

The region’s shared aquifers also face growing populations and decades of overexploitation. Water experts said the border communities need to cooperate and protect the aquifers from overexploitation and pollution — a prospect complicated by the border’s environment.

Groundwater is complicated — it’s hard to describe, tough to measure and the water quality varies across the region.

“Unlike surface water, where we can see when we’re having floods or droughts, groundwater is invisible,” said Sharon B. Megdal, the director for the Water Research Center at the University of Arizona. “A lot of the border communities depend on this pumped water.”

Surface water is managed by treaties, but there’s no current formal agreement on groundwater management between the United States and Mexico on its shared aquifers, Megdal said.

“It’s a hard puzzle. But if we don’t do something, then communities run the risk of overusing their water resources (and) having extraction become much more expensive, because you’re going deeper or having the quality change,” Megdal said.

Geology, hydrology and wells

In past geologic times, rivers or lakes could push into bedrock formations by the shifting of tectonic plates beneath the Earth’s crust. Eventually covered by land, these “fossil” rivers are the basis of the Hueco and Mesilla bolsons, which sit underneath Texas, New Mexico and Chihuahua. Those underground pools are recharged by rainfall that streams off the mountains.

The geologic formations creating the aquifers stretch for miles, across counties, states and the border.

The Hueco Bolson is about 200 miles long and 25 miles wide beneath Texas and into Chihuahua; it has a maximum thickness of 9,000 feet deep. Only the top several hundred feet has fresh water while much of the other water is brackish, or somewhat salty, and the lower portions are extremely salty.

The Mesilla Bolson has a maximu­­m thickness of 2,000 feet, extends 62 miles long and four miles wide under New Mexico and Chihuahua. The two bolsons have little water flowing between one another and are viewed as separate systems.

Rocks are gradually submerged as water is released from the Caballo Dam in New Mexico into the Rio Grande. Mountains and riverbeds make up watersheds that recharge and restore aquifers. (Corrie Boudreaux/El Paso Matters)

The dry, arid desert climate slows the recharge process to about 33,000 acre-feet of water, or about 10 billion gallons a year, from different sources that include mountains, the Rio Grande channel or unlined canals.

Zhuping Sheng, a researcher for the Texas Tech AgriLife Transboundary Aquifer Assessment Program, said accessing that water means drilling wells about 250 feet deep in El Paso.

“Think about a sponge, the water stays in the holes,” Sheng said. “When you pump, basically, water will be squeezed out from that spot.”

Sheng said the simplest way to think of the aquifer is like a savings account for a bank, with withdrawals from pumping, and deposits from injections and natural recharge.

“We continue depleting it –- at a faster rate in dry years, more when there’s less river water -– but we continue withdrawals,” Sheng said.

The biggest pump

Robert Mace, the executive director at the Meadows Center for Water in the Environment at Texas State University, said groundwater law in Texas follows an older English concept, called the rule of capture.

“If I get the groundwater first, before you do, there’s nothing you can do. Another way of putting it is sometimes the ‘law of the biggest pump,’” Mace said. “If I put in my well and I dry your well up, you have no legal recourse.”

Only 10 other states use the rule of capture standard and only a few changes have been made to limit the free-for-all on groundwater. Texas allows local groundwater conservation districts to make rules that supersede the rule of capture. Generally, districts have limits on pumping or spacing requirements to minimize the impacts of pumping on neighbors’ land and water.

El Paso, however, is not governed by a local groundwater conservation district.

In 1998, the Texas Legislature determined that El Paso County was a Priority Groundwater Management Area –- meaning it could be forced to make a local group to regulate groundwater because of current or future declines. After a series of reviews, commissioners at the precursor agency to the Texas Commission on Environmental Quality, the Texas Natural Resource Conservation Commission, wrote at the time that  El Paso “clearly demonstrated a significant effort toward regional cooperation, planning, and voluntary implementation of actions to address water supply problems,” and would not need further oversight from a local district.

Ed Archuleta, who was the CEO of El Paso Water at the time, said TCEQ commissioners determined the utility’s 50-year plan for water management, conservation and pivot to surface water would make another agency redundant.

“In other words, we were already doing a good job of managing the water,” Archuleta said.

The federal government has traditionally been hands-off on groundwater, leaving regulation up to states, Mace said.

“Any discussion of trying to build the groundwater component into the international agreement with Mexico is perceived by many as a potential threat of federal regulation or groundwater resources,” Mace said. “There’s great resistance at a state and even at a local level.”

The freshwater problem

A 2004 study estimated the fresh water in the Texas portion of the Hueco Bolson at 9 million acre-feet, nearly 3 trillion gallons. But even that number fluctuates to as high as 20 million acre-feet, depending on the model used to measure the capacity.

Alex Mayer, who directs the Center for Environmental Research Management at the University of Texas at El Paso, said the first challenge is measuring the aquifer, calling 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-use measurements are based on systems of self-reported data — whether that’s from a utility like El Paso Water to a farmer’s own estimates on crop watering.

“It’s an issue of transparency around the data. It’s very difficult to quantify a resource when you don’t know how much is there, and how much is being removed at what rate,” Mayer said.

Water pours into an irrigation canal near Garfield, New Mexico. The Elephant Butte and Caballo reservoirs were opened in late May to release water for irrigation to southern New Mexico and El Paso. (Corrie Boudreaux/El Paso Matters)

According to Mayer’s estimates, there’s between 30 to 60 years of freshwater left in the aquifer if El Paso and Ciudad Juárez continue in the “business-as-usual manner,” depending on how “optimistic” the climate models look.

Ciudad Juárez’s demand requires that 49 billion gallons be pumped a year, or about 151,000 acre-feet, entirely from the two groundwater basins. That just surpasses El Paso’s usage, despite Juárez having double the population. Both cities agreed to an informal sharing of data between each other, but no formal agreements on water management.

The utility El Paso Water splits supply between groundwater and treated river water for its use of about 118,000 acre-feet average, about 38 billion gallons, within the city each year. The unincorporated portions of El Paso County rely solely on groundwater.

About 40% of the city’s water is pulled from the Hueco Bolson aquifer; it gets another 17% from the renewable Mesilla Bolson aquifer west of the Franklin Mountains, 5% from removing salt out of brine and the Rio Grande provides the remaining 38%.

El Paso Water is pumping 60,000 to 70,000 acre-feet — or between 19 billion and 22 billion gallons — out of the Hueco Bolson every year.

Since the 1990s, the utility has worked to decrease demand and implemented conservation practices to save groundwater.

The utility uses injection wells to return a daily 3 million gallons of treated wastewater into the aquifer. Using a combination of wells and ponds, the utility has put 30 billion gallons back into the ground since the 1990s.

Scott Reinert, the water resources director for El Paso Water, said that’s stabilized the water table, which dropped hundreds of feet in the 1970s and 1980s from over-pumping.

Reinert said the core issue of groundwater depletion isn’t running out of water.

“It’s running out of inexpensive water,” he said.

Cover photo: A diesel powered groundwater pump outside of Fabens. (Danielle Prokop/El Paso Matters) 

Danielle Prokop is a climate change and environment reporter with El Paso Matters. She’s covered climate, local government and community at the Scottsbluff Star-Herald in Nebraska and the Santa Fe New...