Current Status and Future Directions in Modeling a Transboundary Aquifer: A Case Study of Hueco Bolson

The Hueco Bolson aquifer is a binational aquifer shared by the United States of America (USA) and Mexico that is strongly interconnected with the transboundary river, Rio Grande/Rio Bravo. Limited recharge, increasing urbanization, and intensified agriculture have resulted in the over-drafting of groundwater resources and stressed the aquifer, threatening its sustainability if mitigation actions are not taken soon. Research indicates that the aquifer’s hydraulic gradients and flow directions have changed due to the high groundwater withdrawal rates from the two major cities—El Paso (USA) and Ciudad Juarez (Mexico). This paper presents a comprehensive overview of the Hueco Bolson aquifer modeling history and makes a case for future modeling and binational engagement efforts. First, we discuss the evolution of groundwater modeling for Hueco Bolson from the past to recent times. Second, we discuss the main water management issues in the area, including water quality and quantity, stakeholders’ participation, and climate change. To address the challenges of holistic water management, we propose developing a graphical quantitative modeling framework (e.g., system model and Bayesian belief network) to include experts’ opinions and enhance stakeholders’ participation in the model. Though the insights are based on a case study of Hueco Bolson, the approaches discussed in this study can provide new strategies to overcome the challenges of managing a transboundary aquifer.

Investigating Management of Transboundary Waters through Cooperation: A Serious Games Case Study of the Hueco Bolson Aquifer in Chihuahua, Mexico and Texas, United States

Management of transboundary aquifers is a vexing water resources challenge, especially when the aquifers are overexploited. The Hueco Bolson aquifer, which is bisected by the United States–Mexico border and where pumping far exceeds recharge, is an apt example. We conducted a binational, multisector, serious games workshop to explore collaborative solutions for extending the life of the shared aquifer. The value of the serious game workshop was building knowledge, interest, understanding, and constituency among critical stakeholders from both sides of the border. Participants also learned about negotiations and group decision-making while building mutual respect and trust. We did not achieve consensus, but a number of major outcomes emerged, including: (1) participants agreed that action is called for and that completely depleting the freshwater in the shared aquifer could be catastrophic to the region; (2) addressing depletion and prolonging the life of the aquifer will require binational action, because actions on only one side of the border is not enough; and (3) informal binational cooperation will be required to be successful. Agreeing that binational action is called for, the serious games intervention was an important next step toward improving management of this crucial binational resource.

Reinterpreting Models of Slope-Front Recharge in a Desert Basin

Identification of recharge areas in arid basins is challenging due to spatial and temporal variability and complexity of the hydrogeology. This study re-evaluates recharge mechanism in a desert basin where isotopic and geologic data indicated that published conceptual models of recharge are not accurate. A new model of recharge is formulated that is consistent with the unique geologic framework in the basin. In the area of study, the Rio Grande flows across a broad alluvial floodplain, the “El Paso-Juarez Valley”, where the river has incised the surface of the Hueco Bolson. The modern Rio Grande floodplain overlies the older basin fill, or “Hueco Bolson deposits”, in the valley portion of the area. The lateral contact between the older bolson deposits and the recent alluvial floodplain deposits defines the “slope front”. The valley wall along the slope front is penetrated by many arroyos that incise the Hueco Bolson deposits and modern floodplain surface. The presence of a large lens of freshwater at the boundary between the older bolson fill and recent Rio Grande alluvium seemed to suggest to previous researchers that dilute water developed due to runoff drawn in by San Felipe Arroyo, a prominent arroyo at the slope front between the older Hueco Bolson deposits and the recent Rio Grande alluvium. Our follow-up verification work illustrates that this is demonstrably not the case. The testing of groundwater samples for stable water isotopes and radioisotopes showed that the deeper and more dilute waters near San Felipe Arroyo are actually pre-dam waters recharged from the shifting Rio Grande channel.