Water Security at the US-Mexico Border | Part 1: Background

Water security has been a growing concern at the US-Mexico border for decades. But in recent years, the situation has become critical, as persistent droughts, rising demand, and conflicting interests continue to strain two significant transboundary rivers — namely, the Colorado River and the Rio Grande. These rivers alone constitute two-thirds of the border, supplying water to an increasingly populated and industrialized region of the US and Mexico. Those dependent on the dwindling resource are now facing the economic and environmental consequences of unchecked development.  

The Colorado River  

 

Image Credit

Aldrin Ballesteros, Serendipity

 

 

For the past 50 years, nearly every drop of the Colorado River has been consumed as it flows south.  

When the river reaches the Morelos Dam at the US-Mexico border, most of the little remaining water is sent to farmland in Baja California, Mexico. Instead of emptying into the Gulf of California, the river’s remnants now disappear south of the dam, leaving residents and wildlife in Baja California and Sonora with dried riverbed. 

North of the border, signs of stress appear much earlier, however. In the Lower Basin, Lake Powell and Lake Mead reached historic low levels in 2022, falling to just a third of their capacities.  

97% of the Colorado River Basin lies within the US. How the Upper and Lower Basins choose to address a warmer and drier climate, over-extraction, and the manipulation of water flow directly affects the border. 

“In reality, local communities have very little power over water management along the border [...] While it is necessary to have national institutions regulating, managing, and allocating water, there is a clear need for more local community involvement.” 

– Dr. Francisco Valencia-Lara, professor at the School of Transborder Studies at Arizona State University 

The Rio Grande 

 

Image Credit

Aldrin Ballesteros, Serendipity

 

Extreme drought conditions and over-extraction have also caused tension for those dependent on the Rio Grande at the border, as competing water users struggle to meet their own needs. This situation, however, is arguably more contentious.  

Since 1992, Mexico’s water deliveries to the US have been irregular. The current five-year cycle that ends in October 2025 is no different, as the US has only received a little over a year’s worth of water thus far. Texas' agricultural sector has faced significant setbacks from deficient deliveries. Due to the lack of water, the state’s last sugar mill shut down last year. Its citrus industry is also under threat. As a result, Texan politicians have repeatedly threatened to impose sanctions on Mexico. The US State Department’s Bureau of Western Hemisphere Affairs also stated that it would cut Colorado River water deliveries to Tijuana. The recent $280 million grant agreement dedicated to providing economic relief to Rio Grande Valley farmers has only mitigated some tension. 

To make up for past shortfalls, Mexico has used its own storage from the Amistad and Falcon Reservoirs — two major water sources located and shared at the border that are experiencing record lows. Such last-minute decisions have provoked tension in downstream districts, where Mexican residents and farmers are already facing their own domestic water issues.   

Governance and Water Allocations 

The International Boundary and Water Commission (IBWC), also known as the Comisión Internacional de Límites y Aguas (CILA) in Mexico, has been the primary arbiter in such binational debates. Its role is to apply the rights and obligations which the US and Mexico governments assume under treaties and related agreements. The 1944 Water Treaty is a particularly important one, as it expanded the responsibilities of the IBWC and defined water distribution requirements.  

Image Credit

Aldrin Ballesteros, Serendipity

 

Image Credit

Aldrin Ballesteros, Serendipity

 

Image Credit

Aldrin Ballesteros, Serendipity

 

It is important to note that the treaty was created when water from the Colorado River and Rio Grande was not as scarce as it is now. Megadroughts and aridification were not accounted for. 

Obstacles 

The sharing of a finite resource often reveals the complexities of border community interdependence. This is especially the case at the US-Mexico border, where deep structural and institutional asymmetries between the two countries manifest. While the institutional and legal framework of the US finds strength in its local governments, Mexico's framework is much more centralized. Despite the region’s shared water security issues, such polarization has contributed to the many difficulties of achieving cross-border cooperation.  

“[The 1944 Water Treaty] allows for absolutely anything if [the US and Mexico] agree. But that would imply a lot of changes on the Mexico side in terms of management of its water resources and governance schemes. It’s a big responsibility.” 

– Dr. Rosario Sanchez, senior research scientist at the Texas Water Resources Institute 

Nevertheless, it is widely recognized that the border’s water crisis can only be addressed binationally. One path forward is to deepen our understanding of the border region’s unique environmental and socioeconomic conditions that are inextricably tied to the two rivers. Addressing this knowledge gap may provide border communities with the legitimacy needed to garner support from all levels. 

 

Additional Sources

https://www.nature.com/articles/s43247-024-01291-0#Tab2

https://www.e-education.psu.edu/earth111/node/993

https://www.congress.gov/crs-product/R43312

https://www.nadb.org/blog/101-colorado-river-basin-from-the-lens-of-the-us-mx-border