The Mexico City Metropolitan Area (MCMA) is a significant and important urban center in North America, covering an area of approximately 9500 km ² with a population of almost 23 million, yet the water supply remains unsustainable. The total water demand in the MCMA is 84 m ³ /s and is provided by groundwater (63% or 53 m ³ /s), imported water (27% or 23 m ³ /s) and recycled water (10% or 8 m ³ /s). The natural recharge of the MCMA aquifer is approximately 23 m ³ /s, indicating an overexploitation of groundwater resources of approximately 25 m ³ /s (800 Mm ³ annually), a reasonable future goal for recharge in the MCMA. Hydrologic analysis indicates two main opportunities currently to increase water supply in the MCMA: indirect water reuse with recycled water and managed aquifer recharge (MAR) with storm water. An inventory of MAR project case studies in the MCMA summarizes methods for recharge, water sources, geographical distribution, and the main results obtained in each project for the last 80 years. The inventory consists of 21 MCMA area MAR case studies including (1) conceptual, (2) design level, and (3) pilot‐ to full‐scale facilities, only some of which have operated for relatively short periods of time, with one remaining MAR project currently operational. The review found that beyond the technical and economic issues that MAR project design normally address, the existing regulatory framework and the continuous change in water district chairs in charge of the operation and supply of water are significant barriers to increasing MAR in the MCMA.

The Mexico City Metropolitan Area, located within the Mexico Basin, is the most important economic center in Mexico. An ever-growing population, currently at 22 million with increasing water demands, has resulted in the overexploitation of groundwater with associated impacts to hydrological conditions for a century. Land subsidence due to chronic groundwater level declines has damaged infrastructure and increased water delivery and flood control challenges, causing loss of aquifer storage. An additional associated problem is groundwater quality deterioration, which reduces potable supplies due to increasing anthropogenic pollution and salinization. A new integrated conceptual model of the Mexico Basin Aquifer has been constructed based on a comprehensive compilation of existing and new hydrogeological knowledge. As a result, this conceptual model updates and improves the understanding of the characteristics of the aquifer and current hydrodynamic behavior of groundwater. Four hydrogeological units were identified, their heads and related flow system interdependencies were evaluated and their hydraulic properties associated; this allowed identifying local, intermediate and regional flow systems, aquifer transition from confined to unconfined conditions, changes to land subsidence and groundwater quality deterioration. This conceptual model could be the basis in building a numerical model, and as a powerful tool to test different management scenarios for decision-making.

Managed aquifer recharge (MAR) is the umbrella term for a range of technologies that enable the integrated use and management of surface water and groundwater to achieve a wide and growing range of social, economic and environmental benefits. The extent and variety of its applications and benefits have mushroomed in recent years as demonstrated in the suite of papers contained within this Special Issue of Sustainable Water Resources Management. This paper introduces the Special Issue and draws together some insights arising from the findings of these papers. Managed aquifer recharge projects normally evolve through a development cycle that covers planning, investigations, pilot scale trials and then implementation of full-scale projects. This Special Issue starts with four papers that synthesize information from a large number of MAR sites, to demonstrate the scope and geographic distribution of international efforts in MAR, factors affecting the economics of MAR projects, and efforts to find metrics to compare their performance among sites and over time. Then there are four papers describing some significant and widely contrasting completed MAR projects in four continents covering their development, what has been learned and some operational issues. Given this context, the next five papers explore the implementation and evaluation of pilot projects in three countries. These papers address issues ranging from hydrogeological characterization, evaluating impacts on groundwater-dependent ecosystems to community participation. All papers to this point give context to the final five papers that show the planning and preliminary studies performed to select MAR sites, to design pilot projects or to explore the feasibility of large-scale MAR programs. Arranging the sequence of papers in this way is intended to yield an understanding of the need for the investigations and modelling to produce viable projects, and to help readers to consider some important practical questions. What steps are needed for any given project to: define objectives; build partnerships; engage with communities; assemble evidence of technical viability, sustainability and safety; secure funding; design and construct efficiently; streamline operations; and finally to monitor the extent to which a completed project met its goals? These papers were developed out of a broader selection of papers presented at the 9th International Symposium on Managed Aquifer Recharge (ISMAR9), Mexico City, June 2016. They are a companion to another Special Issue arising from ISMAR9, published in the journal Water on the complementary theme “ Water Quality Considerations for Managed Aquifer Recharge Systems” edited by Prof. Dr. Pieter Stuyfzand and Dr. Niels Hartog (2017). These Issues are a contribution of the International Association of Hydrogeologists Commission on Managing Aquifer Recharge ( IAH-MAR ) to the advancement and dissemination of knowledge for wise application of MAR.

The groundwater supply of the city of Chihuahua, Mexico, is currently unsustainable: demand exceeds replenishment in this area of relatively low precipitation and periodic droughts. The Chihuahua basin hydrologic analysis reflects only two areas of opportunity to increase water supply: water reuse and managed aquifer recharge with treated wastewater. This paper presents the results of project studies carried out by the Institute of Engineering of the UNAM (Universidad Nacional Autónoma de México—National Autonomous University of Mexico) to define the best method for managed aquifer recharge (MAR) with treated wastewater and to identify suitable locations. The work was conducted in accordance with the Mexican guidelines for aquifer recharge with treated wastewater (NOM-014; CONAGUA NOM-014-Requisitos para la recarga artificial de acuíferos con agua residual tratada, 2007) and includes geophysical surveys and unsaturated zone modeling to design a pilot test for intermittent infiltration which will subsequently inform the feasibility and design of a large scale system to recharge 25 Mm³/year.

El método APLIS es una herramienta que permite estimar la tasa media de recarga anual en acuíferos carbonatados, procedente de la infiltración de las precipitaciones en los acuíferos. La tasa es expresada como porcentaje de la precipitación, a partir de las siguientes variables: Altitud (A), Pendiente (P), Litología (L), áreas de absorción-Infiltración preferencial (I) y Suelo (S). Para cada variable se han asignado categorías o intervalos, estableciendo un valor entre 1 (mínima influencia en la recarga) y 10 (máxima influencia) y se han almacenado en un Sistema de Información Geográfica (SIG). Esto permite la superposición en el SIG de las capas de información correspondientes a las variables para calcular la tasa de recarga mediante la ecuación R = (A + P + 3·L + 2·I + S) / 0.9 y obtener la distribución espacial de la misma.