The challenge of shared water

By Rosario Sanchez

Little is said about why the availability and access to shared water bodies (rivers, lakes or aquifers) between countries is an issue that should not be overlooked in 2023. The issue is relevant because weather phenomena related to climate change have dramatically decreased water availability in numerous basins around the world in recent decades.

In fact, the issue is so relevant that the risk analysis organization Eurasia Group determined, in a study published in January 2023, that there are different potential geopolitical conflicts in the world that could materialize this year due to increasingly unstable conditions in shared or transboundary international waters. One of these centers on the 21% decrease in the flow of water supplied bythe Colorado River, something that affects the western United States and northwestern Mexico.

The issue for Mexico becomes more important when analyzing the Rio Bravo basin: the level of international dams and Mexico's obligations under the 1944 water treaty have been showing signs of depletion for a couple of years now, and projections of water availability in the basin do not point to a better scenario in the years to come.

In addition, last year, international organizations estimated that in 2023 there will be an increase in extreme drought in different areas of the planet, such as southwestern Europe and North America, with Mexico and the United States being among the most affected, in addition to the Amazon region and Chile.

The issue of shared water between countries is of geopolitical importance because in the face of shortages, especially of surface water, shared groundwater provides about 40% of the world's drinking water, and this is increasing at the same rate as droughts are increasing on the planet. In other words, the greater the drought, the greater the dependence on groundwater, and therefore, the greater the vulnerability of shared water systems.

There are more than 640 shared groundwater bodies around the world, according to a report published in 2021 by UNESCO and the World Meteorological Organization. In Mexico, it is estimated that we share 28 aquifers with the United States, six with Guatemala and one with Belize.

The general problem is that shared groundwater is generally unregulated. There are about 3,000 international agreements that regulate shared rivers (surface water), but there are only seven worldwide that "touch" (not necessarily regulate) groundwater.

The case of the U.S.-Mexico border is no exception. There is no regulatory framework for transboundary groundwater. The 1944 water treaty does not address its regulation and there is only the reference of Minute 242 of 1973 on the Yuma aquifer. This poses restrictions on pumping on both sides of the border to counteract the high salinity indexes of the Colorado River tributary. In other words, there has been no new formal rapprochement between the two countries to address the issue in the last 50 years.

The management of transboundary aquifers worldwide is a pending task -of course, with some exceptions such as the Genoese aquifer; Nubian Sandstone, in Africa, and recently the Guarani, in South America, among the most important ones that have already been considered in treaties.

Whether surface or groundwater - and in the face of global pressure for reserves to cope with persistent drought conditions - it is key to note thattransboundary water management requires the use of various disciplines such as hydrology, hydrogeology and geochemistry to understand the conditions of water systems.

It also requires international law to determine rules for shared use, diplomacy for the exchange of information, confidence building, construction of social infrastructure, effective communication to generate cooperation and even the participation of organizations such as the International Court of Justice (ICJ), which recently handled a dispute between Chile and Bolivia over the right to use the flow of the Silala River.

So this 2023, the management of transboundary bodies of water should be a topic on the table of the binational agenda. I give you just one example in this column: scientists estimate that the upcoming occurrence in the Pacific Ocean of the meteorological phenomenon known as El Niño will bring substantial changes in rainfall and temperature patterns worldwide, as well as in the demand for the liquid for human activities and its use as a means of communication. This means that there will be even more pressure on the availability of internationally shared water reserves, especially those that are not regulated.

In the case of Mexico, the persistent drought conditions in its international basins that have highlighted the limits of the 1944 water treaty, and the estimates of extreme shortages in the coming years, indicate not only an alarm of water security and social vulnerability, but also of national security that, to this day, has not been a priority in the binational agenda. The status quo, or neglect, has been the usual preference. It will only be a matter of time, and not much longer, before the level of scarcity forces us to rethink our priorities.

* She is a Senior Research Scientist, Water Resources Institute, Texas A&M University.

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