Groundwater Shared by Countries Is Knowledge Void

Management of transboundary aquifers is on the United Nations agenda this fall.

Rice fields in the Mekong Delta, near Can Tho, Vietnam. An increase in groundwater irrigation in the region could affect groundwater availability across national borders. Photo © J. Carl Ganter / Circle of Blue

Rice fields in the Mekong Delta, near Can Tho, Vietnam. An increase in groundwater irrigation in the region could affect groundwater availability across national borders. Photo © J. Carl Ganter / Circle of Blue

By Brett Walton, Circle of Blue

The Mekong River Delta is under immense pressure. Upstream, a cascade of dams in China trap water and silt, the building blocks of delta life. Downstream, demand for irrigation water is rising in the world’s rice bowl.

A tough task for any country, managing the delta’s water problems come with an extra degree of difficulty for Cambodia and Vietnam — water use in one country influences water availability in the other.

The ties between the two countries, however, are not solely about surface water. The Mekong Delta sits atop a groundwater system that crosses the political border. Pump too much here and water levels drop way over there, where the national flag is of a different stripe and color. The Mekong River declines too, because the aquifer is an underground drip feed to the river.

In effect, the groundwater resource is shared, especially by farmers in both countries. But management is not. And that omission is a source of budding concern.

In a study published earlier this year, Stanford University researchers found that if irrigated land in Cambodia continues to expand at current rates — a 10 percent increase per year, mostly irrigated by groundwater — the aquifer in neighboring Vietnam will be drawn down and Mekong River flows will be weakened. Such a scenario could cause the land surface to sink, worsen arsenic contamination, and threaten domestic water supplies in the dry season for 1.5 million people who use shallow wells. Laura Erban, a study author who is now a U.S. Environmental Protection Agency hydrologist, called an irrigation expansion in Cambodia a potential “international hazard” for transboundary water resources.

“We’re concerned about arsenic pollution. We’re concerned about cross-boundary conflict over drawing down groundwater levels,” Erban told Circle of Blue.

The Mekong Delta is but one example of a worldwide water management challenge. Despite more than a decade of technical and political attention at the highest international level, countries have made little progress in developing agreements to coordinate the oversight of groundwater resources that cross political borders. Without such agreements water managers operate with blinders on, and risk damaging or polluting aquifers that sustain farms and cities, rivers and ecosystems.

Worse, experts say that scientific understanding of the roughly 600 transboundary aquifers and groundwater bodies — which underlie nearly every country — is so poor that even identifying the basins most vulnerable to conflict, contamination, or depletion is comes down to an educated guess.

“A lack of data and knowledge makes it hard to answer the question,” Gabriel Eckstein, a Texas A&M University professor who studies water law, told Circle of Blue.

Thanks to satellite measurements and intensifying public scrutiny in recent years, the perilous condition of a majority of the world’s largest aquifers has been sketched in greater detail than ever before. The cross-border consequences of groundwater pumping are less often part of the picture. Transboundary aquifers, however, are set to reemerge in the debate. This fall, three years after the topic was last on the agenda, the United Nations General Assembly will discuss principles for managing these basins. Talk will likely focus on two areas: cooperation and data.

Filling the Management Void

Researchers often compare the legal codes and scientific knowledge of transboundary aquifers with those of shared rivers. For rivers, there is a mature and developed body of law, including a United Nations convention that became legally binding in August 2014 for the 36 countries that have ratified it. In the 20th century alone more than 145 river basin treaties were signed, many of them sophisticated measures that allocate water, coordinate reservoir operations, monitor water flows, or account for pollution. “River treaties are serious and complex arrangements for management,” Eckstein said.

The world of transboundary aquifers is much more constrained. Eckstein, a leading legal expert, could count fewer than 10 formal and informal agreements worldwide. Two agreements in northern Africa, for the Nubian and Northwest Sahara aquifers, facilitate the sharing of data. An agreement signed in 2015 between Jordan and Saudi Arabia prohibits groundwater use in a “protected area” of the Al-Sag/Al-Disi Aquifer, the first agreement of its kind. An agreement on the Guarani Aquifer has been signed but not yet ratified by the four countries that overlie it.

Only one aquifer, the Genevese, shared by France and Switzerland, can be considered a true management agreement, according to Eckstein. The agreement, signed in 2007, sets an annual limit on water pumping, which is governed by a joint French-Swiss commission that has the authority to monitor water withdrawals and aquifer levels.

Observers give several reasons for the slow progress in developing similar agreements elsewhere. First, groundwater moves gradually through rock and soil, which means problems set in motion today may not reveal themselves for a decade or more. Aquifers are also famously complex systems, not a pool of underground water, but a network of interconnected, saturated sediments. No two are alike.

Second, according to Raya Stephan, an international water law consultant, is the fact that politics tends to lag behind science.

“When working with technicians and scientists, it does not seem complicated,” Stephan told Circle of Blue. “They are ready to share information and work together. But when you get to the political story, it is still difficult for politicians to understand that it is in their interest to cooperate with their neighbor.”

Data Is the Missing Foundation

Of the hundreds of groundwater basins without a management agreement, how many ought to negotiate one? That is an open and important question that cannot be answered without a better understanding of the resource, says Neno Kukuric, director of the International Groundwater Resources Assessment Center (IGRAC).

“We don’t know how many agreements are needed because we don’t know the situation underground in many places,” Kukuric told Circle of Blue. If an aquifer is in an unpopulated area or not at risk of pollution, then it might only need to be monitored rather than formally managed. Even then, the countries will need to coordinate a monitoring program.

Understanding these distinctions is a goal of IGRAC, a research center under the United Nations umbrella. IGRAC publishes the definitive global map of transboundary aquifers.

The map project has come a long way. The first version, published in 2009, “was just circles” that represented aquifers, Kukuric recalled. “Now we have delineated boundaries,” he says.

IGRAC's transboundary aquifer map shows that nearly every country shares a groundwater basin with a neighbor. For an interactive version of the map, click here.

IGRAC’s transboundary aquifer map shows that nearly every country shares a groundwater basin with a neighbor. For an interactive version of the map, click here.

Those boundaries are constantly being revised. The 2009 map showed 279 aquifer “circles.” In the 2015 update, the number had grown to 366 aquifers and 226 groundwater bodies, an administrative term used by the European Union for basins within Europe.

Many of the characteristics of these aquifers — how water moves within the rock layers, how much water is pumped, where it is recharged, the chemistry — are essential for management but unknown to researchers. Erban called her study in the Mekong, which relied on satellite data to gauge irrigated area, a “first effort” but acknowledged that “we have really weak understanding right now” of the underground hydrology and patterns of water use.

Even a political boundary as carefully scrutinized as the Mexico-United States border can be a black box for groundwater knowledge. Researchers do not have a firm grasp of exactly how many aquifers cross the border. Some studies claim eight, while others identify as many as 36. It does not help that there is no internationally recognized standard for defining aquifer boundaries.

In a paper published in January, Eckstein and his colleagues took a different approach. They surveyed existing data and assigned a confidence measure to the candidate Mexico-U.S. aquifers. They found reasonable confidence that 16 aquifers span the border; some confidence for eight, and limited confidence for 12. The exercise confirmed the need to coordinate research, monitoring, and scientific analysis and to standardize geological definitions of aquifers. Transboundary groundwater between two countries is a “conceptual and institutional void,” they stated in the paper.

The uncertainty is due in large part to scientific methods that are not in alignment. Sharon Megdal and Chris Scott saw that first hand. Megdal and Scott are professors at the University of Arizona and members of a binational research team that completed a hydrological assessment of two aquifers along the border of Arizona and Sonora, a Mexican state.

Before the assessment began, researchers from both sides had to harmonize their mapping techniques: confirming that this rock layer is part of the aquifer and that rock layer is not. Otherwise the maps would be disjointed, like a road that buckled during an earthquake. Driving on such a road is nearly impossible and forecasting hydrological changes with such a skewed map has the same chance of success. Getting the definitions in sync required significant deliberation, Megdal recalled.

For Scott, the process underscored how distant a goal management is, when science is at such a rudimentary stage. “It’s a complicated jigsaw puzzle,” he told Circle of Blue. “And we’re not even talking about [management] agreements. We’re just talking about assessment.”

Bringing Parties Together

The United Nations is the most prominent organization advocating for groundwater cooperation. As for rivers, the UN has been instrumental in lifting transboundary aquifers onto the global agenda. IGRAC is involved in a number of data collection, monitoring, and governance projects, from the Balkans to Southern Africa and Central Asia.

“We build trust through common activities,” Kukuric said. “Then the next step is to build a collaborative mechanism.” In the Balkans that mechanism was a committee with representatives of each country. The group spent two years completing studies and assessments of the region’s karst aquifers. “We’re very pleased with the success,” Kukuric said.

The UN is also active in the legal sphere. In 2002, the International Law Commission, a branch of the organization that develops international legal norms, began working on transboundary aquifers. By 2008 the commission had drafted 19 articles on management and monitoring of shared groundwater.

The articles, however, remain in draft form. The General Assembly discussed them in 2011 and again in 2013. Now the articles are back on the agenda.

Stephan, who helped write the draft articles as a consultant with the ILC, said that governments are less likely to want a legally binding convention for aquifers as there is for shared rivers. The process of negotiating and ratifying a convention is arduous. An alternative is for the articles to become internationally recognized guidelines through gradual acceptance and incorporation into bilateral agreements. The UN Human Rights Declaration, Stephan notes, achieved its moral and legal force in this way.

Eckstein also says not to expect any groundbreaking developments in Manhattan this fall. International groundwater law is still too new and, unlike river treaties, there are few legal precedents to establish firm legal guidance.

“There is so little experience with how to manage an aquifer in a transboundary context that most nations would probably be hesitant to commit to any definitive rules,” Eckstein said.

Instead, the countries will do what they have done in the past: discuss the articles and sign a resolution that urges governments to pay attention to the principles and incorporate them, when possible, into local agreements. “That would give [the governments] more time to consider the norms articulated in the draft articles, and maybe even test drive some of them in short-term arrangements with neighboring countries,” Eckstein explained.