Commentary by Dr. Samuel Sandoval Solis
Background
Water deliveries from Mexico to the United States are at their lowest historical levels. It is essential to analyze Mexico’s current water deliveries to the U.S. (Figure 1), which are monitored by the International Boundary and Water Commission (IBWC) and its Mexican counterpart, the Comisión Internacional de Límites y Aguas (CILA).
This figure illustrates the critical situation faced by the basin. Although 2024 has been exceptionally dry, and previous years were below average, Figure 1 shows that almost no water flows from Mexico’s six tributaries into the Rio Grande’s main channel, except under extreme rainfall conditions, such as during the 2022 rainy season. As of November 9, 2024, Mexico has delivered 426.8 thousand acre-feet (TAF), equivalent to 527 million cubic meters, representing approximately 1.2 years of water deliveries, under the fifth and final year of the 36th five-year cycle.
Compliance with Previous Commitments
Minute 331 builds upon its predecessor, Minute 325, addressing challenges faced during two consecutive five-year cycles (#34 and #35). Mexico incurred a water debt during cycle 34 and narrowly met its delivery obligations during cycle 35 by utilizing water reserves stored in international reservoirs. We commend the collaborative efforts of the IBWC and CILA to improve water resource management in the Rio Grande Basin.
Strengthening Binational Groups (Resolutions 1 to 4)
Positive Aspects
We celebrate the creation and strengthening of binational working groups, including the Rio Grande Projects Group and the Rio Grande Environmental Group. These groups represent a proactive, collaborative approach to addressing critical challenges in the basin.
Resolution 2 is particularly significant as it establishes the Rio Grande Environmental Group to provide recommendations on international environmental concerns affecting the river. For years—if not decades—efforts have focused on protecting the environment and improving the poor ecological conditions of the Rio Grande. Over the past four years, the riverbed has dried up twice in the Big Bend region, underscoring the urgent need for environmental advocacy. It is encouraging to see environmental concerns now have a dedicated voice in binational discussions.
Resolution 3 emphasizes water quality through the Lower Rio Grande Water Quality Initiative. The hypersaline Laguna Madre and its estuary will continue to affect water quality in the lower Rio Grande until the river permanently reconnects to the Gulf of Mexico. Addressing these persistent water quality challenges requires restoring this connection.
Resolution 4 highlights the importance of effective coordination among all working groups (Rio Grande Projects, Environmental, Hydrology, and Public Policy). This resolution fosters the commitment to unify efforts across the basin, ensuring diverse expertise and perspectives contribute to effective solutions.
Areas for Improvement
While these resolutions represent progress, public participation remains an area for opportunity. A broader range of scientists, NGOs, universities, and water operators on both sides of the border are now involved, and participation has increased significantly with the creation of new working groups. However, opportunities remain to enhance processes for public and independent expert engagement and communication of negotiation progress.
Transparency is also essential for these working groups. Public access to agendas, meeting minutes, and discussion summaries would not only improve accountability but also ensure that taxpayers—who finance these efforts—stay informed about the topics addressed and the agreements reached. Transparency and inclusion would strengthen public trust and responsibility in the process.
Additionally, the mention of “new water sources” in the Minute raises concerns. Beyond the proposed investment projects (e.g., improving irrigation efficiency), this philosophy appears to perpetuate the current over-allocation of water rather than addressing the root cause: excessive water use. Increasing water supplies addresses symptoms but not the underlying problem; it may provide temporary relief but worsen the situation long-term by increasing water demand. The real issue facing the Rio Grande is over-allocation. The solution —though difficult and painful— is to reduce water use for all users in both Mexico and the United States.
The basin has water, but not enough to meet all imposed demands, especially those prioritizing unsustainable practices like large-scale industrial agriculture in arid regions. There is water for cities and communities, and for the environment, but not enough to sustain large-scale farming operations producing crops like alfalfa and sorghum for livestock feed or niche crops like pecans. Addressing over-allocation is critical to ensuring the long-term sustainability of the Rio Grande.
Analysis of Wet Years and Storage in International Reservoirs (Resolution 5)
To understand Resolution 5 of Minute 331, it is essential to consider the historical context. Since the first cycle under the 1944 Water Treaty began (October 1, 1953), Mexico and the United States have engaged in a kind of “cat-and-mouse game” regarding water storage in international reservoirs.
Mexican authorities, such as CONAGUA, often wait for hurricanes or heavy rainfall to fill reservoirs, while simultaneously managing the system to deliver water obligations to the United States as close as possible to the fifth year—1,750 TAF per five-year cycles (2,159 million cubic meters per cycle). In contrast, the United States attempts to maintain low storage levels in both international reservoirs to ensure room for additional water during rain events and prevent reservoirs from filling, which would restart a new cycle.
In past decades, when water use was lower and intense rainfall was more frequent, international reservoirs occasionally reached full capacity (e.g., during Cycles 12-15 in 1981, 17-19 in 1987, 21-22 in 1991, and 31-33 in 2010). During these wet periods, the United States stored water beyond its assigned capacity in Amistad Reservoir, temporarily using Mexican storage. Once Amistad overflows into Falcon Reservoir, both reservoirs can fill, and the treaty cycle resets. To prevent frequent cycle resets during prolonged wet periods (which can last from one to six months), both sections of the IBWC often temporarily increase conservation storage levels, delaying the treaty cycle reset.
Positive Aspects
Resolution 5 seeks to develop Standard Operating Procedures (SOPs) or guidelines to address this recurring issue. This represents a positive step, as it formalizes an approach to managing these situations more effectively.
Although proactive measures are always welcome, the reality is that it may take years—or even longer—for both reservoirs to reach full capacity again, if at all. Currently, Amistad and Falcon report 21% and 12% of their storage capacity, respectively. Considering the rainy season has ended and storage levels are so low, it is unlikely these reservoirs will fill in the near future. While this clause reflects forward-thinking intentions, its applicability under current conditions may be limited.
Ensuring Reservoirs in the Six Mexican Tributaries Release Water to Fulfill Treaty Obligations (Resolution 6)
Resolution 6 addresses the requirement for Mexico to release water from reservoirs exceeding their Normal Conservation Capacity (NAMO) to fulfill treaty obligations, whether for the current or previous cycles. This clause seeks to ensure that surplus water from the six Mexican tributaries reaches the Rio Grande, as stipulated in the treaty.
Positive Aspects
This clause represents a practical step toward fulfilling treaty obligations. In theory, surplus water from the six Mexican tributaries should reach the Rio Grande’s confluence. However, this often has not been the case, particularly with La Boquilla Reservoir in Chihuahua, where local farmers’ opposition has frequently hindered compliance with treaty requirements. Ensuring that reservoirs in the six Mexican tributaries contribute to treaty obligations is a practical measure to improve water management between the two countries.
What Can Be Improved?
The primary challenge lies in implementing an effective on-the-ground mechanism to ensure compliance with this resolution. Operational control of reservoirs is crucial to make this clause actionable. For instance, in October 2021, farmers in Chihuahua physically took control of the La Boquilla Reservoir to prevent water releases. This incident illustrates the significant challenges of enforcing this resolution.
Summary of Minute 234 (Resolutions 7 to 10)
Resolutions 7 and 8 reiterate provisions from Minute 234 and the 1944 Treaty (Article 9.e), specifying that Mexico can meet its water delivery obligations to the United States through:
- Contributions from two-thirds of the water from the six Mexican tributaries reaching the Rio Grande,
- Transfers of stored water from international reservoirs, and
- Contributions from the San Juan and Alamo Rivers.
This is contingent on Mexico not needing or being able to use the water and providing advance notice to the United States, which must be able to store or use the water. Additionally, Mexico must maintain a one-year supply of water in international reservoirs for domestic and municipal uses along the border.
Positive Aspects
Minute 234 provides a range of strategies for Mexico to meet its treaty obligations, and Resolutions 7 and 8 serve as reminders of these options.
What Can Be Improved?
Rather than focusing on improvements to these two resolutions, the key question is: what are the potential implications of this Minute once these strategies are applied?
While Minute 331 only provides strategies for sending water from Mexico to the United States to fulfill treaty obligations (considering part or all the water from the six Rio Grande tributaries, reservoir storage, and other tributaries like the San Juan and Alamo Rivers), once these tools are used and given the over-allocation of the basin, only municipal water for the Mexican side will be guaranteed for one year. All other water could be used to meet U.S. treaty obligations, potentially impacting water allocations for other users, particularly agricultural users.
Similarly, although the Minute specifies that water from the San Juan and Alamo Rivers can only be used if Mexico does not need it, the challenge lies in the timing of allocations. For example, this year, the El Cuchillo or Marte R. Gómez Reservoirs may have sufficient water to meet U.S. treaty obligations, but this water might be needed in the future for Monterrey or farmers in the Lower San Juan River Basin. This will place additional pressure on improved planning, management, and water use efficiency, particularly for Mexico’s agricultural sector, which relies on these reserves.
If Mexico transfers water to the United States from international reservoirs or from two-thirds of the water from the six tributaries to meet treaty obligations, it is highly likely that water allocations for farmers in Tamaulipas (particularly in Irrigation District 025 Bajo Río Bravo) will be reduced. Historically, water transfers from international reservoirs to the United States have disproportionately affected farmers in Tamaulipas, as seen during Minute 325, and this issue will continue to present significant challenges towards the future.
Minute 331 defines “excess water from reservoirs” as water stored above the Maximum Operational Water Level (NAMO). This water would be available for delivery to the United States. For example:
- El Cuchillo Reservoir
- Primary source of water for Monterrey.
- Storage capacity: 1,784 million cubic meters (MCM).
- NAMO: 1,123 MCM.
- The difference between total capacity and NAMO (661 MCM) is used to prevent flooding. During the dry season (November to May), the reservoir often stores water above NAMO to prepare for the following year’s needs.
However, under the new provisions of Minute 331, this excess water stored above NAMO could be transferred to the United States. While this water is typically conserved for future urban needs, its use to meet treaty obligations would pressure Mexico to adjust its water management practices.
- Marte R. Gómez Reservoir
- Primary source of water for Tamaulipas farmers in Irrigation District 026 Bajo Río San Juan.
- Storage capacity: 2,304 MCM.
- NAMO: 1,160 MCM.
- The difference between total capacity and NAMO (1,144 MCM) is also used to prevent flooding. During the dry season, this water is stored for agricultural irrigation.
As with El Cuchillo, this stored water is critical for future agricultural cycles, particularly during planting seasons. Under Minute 331, the excess water above NAMO could be reallocated to fulfill U.S. treaty obligations, directly impacting farmers dependent on these reserves.
In both reservoirs, water stored above NAMO is not immediately unusable. Typically, it is strategically conserved for future needs. However, under Minute 331, Mexican users—both urban and agricultural—will need to adjust their practices, as this excess water may now be directed to the United States to meet treaty obligations.
This change increases the pressure on Mexico’s governance systems, reservoir operations, and water allocation processes. The demand for short-term planning and administration have grown exponentially.
Pending issues
Beyond these short-term strategies, there remains a more critical issue: the persistent reduction of water contributions from the Rio Conchos Basin in Chihuahua to meet treaty obligations. As shown in Figure 2, five of the six Mexican tributaries (Arroyo Las Vacas, San Diego, San Rodrigo, Río Escondido, and Río Salado) have maintained consistent contributions since the treaty’s first cycle. The exception is the Rio Conchos, where increased water use, illegal diversions, and lack of willingness to release water from reservoirs have undermined Mexico’s ability to meet its treaty commitments. This scenario could extend to other tributaries as water scarcity and over-allocation become more pressing issues on both sides of the border.
Figure 2: Contributions of the Six Mexican Tributaries to the United States
This figure illustrates the variability of water flows from the Arroyo Las Vacas, San Diego, San Rodrigo, Río Escondido, Río Salado, and Río Conchos rivers. Historical data highlights the disparities in their contributions.
Defining “Extraordinary Drought” and Its Criteria
Although the treaty allows Mexico to invoke “extraordinary drought” provisions, the criteria for doing so remain undefined. Lessons from the Colorado River Basin and the upper Rio Grande Basin suggest that potential reductions in Mexico’s allocations to the U.S could be assessed. Developing clear scenarios and definitions for “extraordinary drought” would benefit all users, considering the basin’s current conditions and over-allocation.
What Happens if Mexico Exceeds Water Deliveries for Cycle 36? (Resolution 11)
This resolution addresses the scenario in which Mexico exceeds its obligation of delivering 1,323 TAF (1,631 MCM) by October 25, 2025, through contributions from two-thirds of the six Mexican tributaries or transfers from international reservoirs. If this occurs, any excess water delivered would be credited to the next treaty cycle. However, this provision applies only to the current cycle.
Positive Aspects
Clear rules for managing excess water deliveries are beneficial. This ensures that any surplus contributions are accounted for and carry value into the next cycle.
What Can Be Improved?
While practical, the likelihood of Mexico exceeding its water delivery obligations under current conditions is extremely low. Given the persistent challenges in meeting treaty commitments, this clause may have limited relevance in the short term.
Exploring Water Conservation Measures (Resolution 12)
This resolution proposes exploring and detailing water conservation measures in a future Minute. It also hints at potential U.S. investment to support the implementation of these measures.
Positive Aspects
Promoting water conservation measures that reduce consumptive use in the basin is a step in the right direction.
What Can Be Improved?
While the intention to promote water conservation is commendable, past experiences with similar initiatives, such as Minute 309, reveal unintended consequences. Investments in irrigation efficiency often lead to the expansion of agricultural lands, or shifts to water-intensive crops (e.g., pecans).
These actions negate the anticipated water savings. Future conservation measures must include safeguards to ensure that water savings are not offset by increased agricultural demand.
Expiration Date (Resolutions 13 and 14)
These resolutions establish the expiration date of Minute 331: November 6, 2029.
The U.S. is Not Expanding Its Water Allocation (Resolution 15)
This resolution reiterates that the United States is not expanding its allocation of water from the Rio Grande.
Another Minute Will Be Developed Before December 2029 (Resolution 16)
Future Minutes will explore strategies to improve the reliability of Mexico’s water deliveries to the United States.
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Suggested Article: Explanation of the Reduction in Mexico’s Colorado River Water Allocation Under the 1944 Treaty: Minutes 330 and 323.
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Disclaimer. The opinions expressed in this publication are those of the author. They do not purport to reflect the opinions or views of the Permanent Forum of Binational Waters or its members.
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