Journal Articles

The impact of climate uncertainties is already evident in the border communities of the United States and Mexico. This semi-arid to arid border region has faced increased vulnerability to water scarcity, propelled by droughts, warming atmosphere, population growth, ecosystem sensitivity, and institutional asymmetries between the two countries. In this study, we assessed the annual water withdrawal, which is essential for maintaining long-term sustainable conditions in the Santa Cruz River Aquifer in Mexico, which is part of the U.S.–Mexico Transboundary Santa Cruz Aquifer. For this assessment, we developed a water balance model that accounts for the water fluxes into and out of the aquifer’s basin. A central component of this model is a hydrologic model that uses precipitation and evapotranspiration demand as input to simulate the streamflow into and out of the basin, natural recharge, soil moisture, and actual evapotranspiration. Based on the precipitation record for the period 1954–2020, we found that the amount of groundwater withdrawal that maintains sustainable conditions is 23.3 MCM/year. However, the record is clearly divided into two periods: a wet period, 1965–1993, in which the cumulative surplus in the basin reached ~380 MCM by 1993, and a dry period, 1994–2020, in which the cumulative surplus had been completely depleted. Looking at a balanced annual groundwater withdrawal for a moving average of 20-year intervals, we found the sustainable groundwater withdrawal to decline from a maximum of 36.4 MCM/year in 1993 to less than 8 MCM/year in 2020. This study underscores the urgency for adjusted water resources management that considers the large inter-annual climate variability in the region.

In Mexico, one hundred of the 188 most important aquifers dedicated to agriculture and human consumption are over-exploited and 32 are a ected by seawater intrusion in coastal areas. Considering that Mexico relies on groundwater, it is vital to develop a portfolio of alternatives to recover aquifers and examine policies and programs regarding reclaimed water and stormwater. Managed Aquifer Recharge (MAR) may be useful for increasing water availability and adapting to climate change in semi-arid regions of Mexico. In this paper, we present an overview of water recharge projects that have been conducted in Mexico in the last 50 years, their methods for recharge, water sources, geographical distribution, and the main results obtained in each project. We found three types of MAR e orts: (1) exploratory and suitability studies for MAR, (2) pilot projects, and (3) MAR facilities that currently operate. This study includes the examination of the legal framework for MAR to identify some challenges and opportunities that Mexican regulation contains in this regard. We find that beyond the technical issues that MAR projects normally address, the regulatory framework is a barrier to increasing MAR facilities in Mexico.

Abstract: In the parched Upper Santa Cruz River Basin (USCRB), a binational USA–Mexico basin, the water resources depend on rainfall-triggered infrequent flow events in ephemeral channels to recharge its storage-limited aquifers. In-situ data from the basin highlight a year-round warming trend since the 1980s and a concerning decline in average precipitation (streamflow) from 1955–2000 to 2001–2020 by 50% (87.6%) and 17% (63%) during the winter and summer, respectively. Binational sustainable management of the basins water resources requires a careful consideration of prospective climatic changes. In this article we review relevant studies with climate projections for the mid-21st century of four weather systems that affect the region’s precipitation. First, the North American Monsoon (NAM) weather system accounts for ~60% of the region’s annual rainfall. The total NAM precipitation is projected to decline while heavy rainfall events are expected to intensify. Second, the frequency of the pacific cold fronts, the region’s prevalent source of winter precipitation, is projected to decline. Third, the frequency and intensity of future atmospheric rivers, a weather system that brings winter rainfall to the region, are projected to increase. Fourth, the frequency and intensity of large eastern pacific tropical cyclones (TC) are expected to increase. On rare occasions, remnants of TC make their way to the USCRB to cause storms with considerable impact on the region’s water resources. In contrast to the high confidence projections for the warming trend to persist throughout the mid-21st century, the precipitation projections of these four weather systems affecting the region encompass large uncertainties and studies have often reported contradicting trends. An added source of uncertainty is that the USCRB is located at the periphery of the four rain-bearing weather systems and small mesoscale changes in these weather systems may have accentuated impacts on their edges. Despite the high uncertainty in the projections of future precipitation, the early 21st century drying trend and the projected mid-21st century decline in precipitation events serve as a pressing call for planning and actions to attain sustainable water resources management that reliably satisfies future demands.

Keywords: Santa Cruz River; climate change; water resources; transboundary aquifer; transboundary aquifer assessment; Arizona; Sonora

Abstract:Sharing scientific data and information is often cited within academic literature as aninitial step of water cooperation, but the transfer of research findings into policy and practice is oftenslow and inconsistent. Certain attributes—including salience, credibility, and legitimacy of scientificinformation; iterative information production; and sociocultural factors—may influence how easilyscientific information can be used in management and policymaking. However, transnationalityusually complicates these sorts of interactions. Accordingly, we argue that the production of scien-tific information and transboundary water cooperation build upon each other bidirectionally, eachinforming and enhancing the other. We employ a case-study analysis of the Transboundary AquiferAssessment Program (TAAP), a binational collaborative effort for scientific assessment of aquifersshared between Mexico and the United States. Here, information sharing was possible only by firstcompleting a formal, jointly agreed-upon cooperative framework in 2009. This framework resultedin a collaborative science production process, suggesting that the relationship between sharing dataand information and transboundary groundwater governance is iterative and self-reinforcing. Inkeeping with the publication of the TAAP’s first binational scientific report in 2016, we demonstratethe bidirectional relationship between science production and water governance in the TAAP andexplore remaining challenges after scientific assessment.

Arguably, managing water separately from land was one of the great missteps of the 20th century. Turning our eyes to past practices, and recognizing the role watersheds play in the health of the environment and our communities, we see that land and water must be managed together as integrated social-natural systems. This issue of Water Resources IMPACT is a companion to the AWRA 2021 Virtual Summer Conference: Connecting Land & Water for Healthy Communities, convening in July 2021. As co-chair of the AWRA Integrated Water Resources Management Technical Committee, and in partnership with the team at the Babbitt Center for Land and Water Policy, I am proud as guest editor to share these stories and examples of how land use managers and water managers are rediscovering the power of partnering for the benefit of people and the environment.

ABSTRACT: Assessing groundwater resources in the arid and semiarid borderlands of the United States and Mexico represents a challenge for land and water managers, particularly in the Transboundary Santa Cruz Aquifer (TSCA). Population growth, residential construction, and industrial activities have increased groundwater demand in the TSCA, in addition to wastewater treatment and sanitation demands. These activities, coupled with climate variability, influence the hydrology of the TSCA and emphasize the need for groundwater assessment tools for decision-making purposes. This study assesses the impacts of changes in groundwater demand, effluent discharge, and climate uncertainties within the TSCA from downstream of the Nogales International Wastewater Treatment Plant to the northern boundary of the Santa Cruz Active Management Area. We use a conceptual water budget model to analyze the long-term impact of the different components of potential recharge and water losses within the aquifer. Modeling results project a future that ranges from severe longterm drying to positive wetting. This research improves the understanding of the impact of natural and anthropogenic variables on water sustainability, with an accessible methodology that can be globally applied.

ON SEPTEMBER 10·11, 2017 AWRA's international conference "Cutting-Edge Solutions to Wicked Water Problems" was held at Tel Aviv University's beautiful Porter School of Environmental Studies building. Convened in partnership with the Water Research Center at Tel Aviv University, this conference focused on water problems that are difficult to formulate and solve.

American Water Resources Association

This project aims to evaluate the potential of reused grey water in concrete and mortar in order to preserve fresh water for drinking purposes. Using both Treated Grey Water and Raw Grey Water (TGW and RGW, respectively) led to a significant increase in the initial setting time and a decrease in the concrete slump value. In addition, there was no effect on mortar soundness properties. The mortar and concrete compressive strength results obtained at 7 days moist curing time showed a significant increase. Mortar and concrete mixes using TGW cast at curing times of 28, 120, and 200 days led to no significant effects on compressive strength. On the contrary, the RGW achieved slightly negative impact on compressive strength at all curing ages. According to the American Society for Testing and Materials (ASTM C109), TGW and RGW are suitable for mortar and concrete production. Furthermore, these results are in harmony with established requirements for ASTM C94.

In conclusion, TGW and RGW are potential alternatives for fresh water in the concrete manufacturing industry.

In collaboration with city, county, and academic institutions can open new opportunities to secure new water resources. Green infrastructure is critical to reducing the demand on potable supplies, explain authors Susanna Eden at the University of Arizona Water Resources Research Center and at the Pima County Regional Flood Control District.

Water harvesting has been used in the Tucson, Arizona region since prehistoric times and is now in resurgence. Within the past 30 years, Tucson has become a leader in desert rainwater and stormwater capture to build resilience and address growing concerns about water scarcity. Beginning with grassroots efforts focused on collective impacts of individual and neighborhood actions, a new attitude toward rainfall as a resource is flourishing. Local programs encourage citizen participation and support small-scale, distributed infrastructure, with an emphasis on retrofitting properties and roadways, while a large-scale stormwater harvesting project collects enough water to irrigate a regional sports park

The interconnectivities of groundwater to food, energy, and the climate are addressed to various degrees at the state level. Groundwater governance in the United States is decentralized, resulting in considerable variations in state practices. This article, published in Jurimetrics and written by Sharon B. Megdal and Jacob Petersen-Perlman, reports on two state-level surveys and three regional case studies conducted to better understand groundwater governance strategies and practices. The article also relates the results of these research efforts to food, energy, and climate. The analysis points to the importance of identifying best practices for addressing nexus challenges for groundwater.

Citation: Sharon B. Megdal & Jacob D. Petersen-Perlman, Decentralized Groundwater Governance and Water Nexus Implications in the United States, 59 JURIMETRICS J. 99-119 (2018).