Adrián Pedrozo-Acuña

Water security in rapidly urbanising river basins is increasingly threatened by untreated city effluents, industrial discharges, and legacy agricultural contamination. The Tula River basin in central Mexico illustrates this issue, absorbing the majority of Mexico City’s effluent while sustaining a heavily exploited aquifer beneath one of the nation’s largest irrigation districts. This study provides an integrated assessment of surface water and groundwater quality throughout the basin, including the Endhó Dam and its associated aquifer. Water quality analysis revealed severe surface water contamination (WQI > 300), driven by untreated sewage and inadequate sanitation infrastructure. Elevated COD, BOD, and nutrient concentrations indicate significant organic loading and eutrophication risk. Near Tula City, arsenic, copper, and zinc were detected at levels posing direct risks to human health. Groundwater quality was comparatively favourable, with 71% of wells recording WQI < 100; however, arsenic exceeded permissible limits more than twentyfold in select wells, attributed to geological sources. The detection of SVOCs in both hydrological compartments confirms cross-compartment contamination. Point-source reduction alone is insufficient for aquifer recovery; comprehensive sanitation strategies and long-term monitoring are urgently required. These findings carry direct relevance for water governance in megacity-dependent basins globally, where urban, agricultural, and geological stressors demand integrated management approaches.

This study presents an integrated assessment of surface water and groundwater quality in the Tula River basin, Mexico, encompassing the Endhó Dam and its associated aquifer. Water quality index (WQI) analysis revealed severe contamination along the Tula River (WQI >300), driven primarily by untreated sewage discharges from Mexico City and inadequate regional sanitation infrastructure. Elevated concentrations of COD, BOD, and nutrients indicate significant organic loading and eutrophication risk across aquatic ecosystems. Near Tula City, heavy metals including arsenic, copper, and zinc were detected at levels posing direct risks to human health. Groundwater quality was com-paratively favorable, with 71% of sampled wells recording WQI < 100; however, arsenic concentrations exceeding permissible limits by more than twentyfold were identified in select wells, attributed to geological sources. Semi-volatile organic compounds (SVOCs) were detected in both hydrological compartments, confirming cross-compartment con-tamination and highlighting the need for contaminant transport and fate modelling. The inertial contamination trajectory of the aquifer indicates that point-source reduction alone is insufficient for remediation. Comprehensive sanitation strategies, including pre-discharge treatment of Mexico City effluents, alongside proactive long-term aquifer monitoring and remediation programs, are urgently required to safeguard water sup-plies, public health, and ecological integrity in the Tula Valley.

Since 1965, Mexico has dominated global avocado production, with intensification occurring in the water-scarce regions of Michoacan in recent decades, resulting in considerable environmental consequences. This study analyses changes in land use within three major avocado-producing watersheds and examines how these changes affect regional water availability. Supervised LANDSAT image classification indicated a 168% increase in avocado cultivation and a 59% reduction in forest cover from 1993 to 2023. The Gravity Recovery and Climate Experiment (GRACE) satellite data (2002–2023) reveals a notable decreasing trend in total water storage (TWS) (p > 0.05) and a strong correlation (r = 0.81) between the normalised annual data for TWS, deforestation, and avocado expansion. Furthermore, employing an average water footprint of 1,425.81 m3 t−1 for avocados, this study approximates that in 2020, avocados would require roughly 5,500 Mm3 of water, significantly exceeding the estimates of 2,400 Mm3 based on officially recorded production areas and surpassing the total volume of runoff and recharge, which is 3,406.49 Mm3. Thus, conservative estimates indicate that the crop required at least 70% of the region's available freshwater. These findings highlight the unsustainable water consumption and deforestation associated with avocado production, raising urgent concerns regarding regional water security and sustainability.

The aim of this study is to characterise environmental impacts associated with mining operations in the Sonora River basin, a water-scarce region of Mexico. The focus is on evaluating water availability, water quality, and sediment composition along the river. Furthermore, the quality of groundwater for human consumption is assessed. Data collected from an extensive field campaign is employed for this purpose. For the first time, measurements of groundwater levels in conjunction with satellite data have shown a substantial decline in groundwater levels in the northern part of the Sonora River basin, near the Buenavista del Cobre mine, highlighting how mining activities are directly affecting the loss of groundwater resources. Results relative to heavy metal pollution in the river’s surface water indicated the presence of hazardous metals at health-concerning concentrations in two areas in the river basin’s central region. Both assessed indices, the contamination degree factor and the Metal Evaluation Index, demonstrated significant heavy metal pollution associated with mining operations. Moreover, the sediment analysis clearly reveals various areas and mechanisms of heavy metal contamination within the watershed. The Pollutant Load Index (PLI) and the Ecological Risk Index (ERI) indicated significant ecological danger and severe contamination near a mine and in two regions where sediment deposition occurs (as evidenced by ERI > 300 and PLI > 3). This suggests a diffusive contamination process that conveys metals from the northern section of the basin to the southern areas of the Sonora River, due to the steeper slopes of upstream rivers. Lastly, groundwater sources intended for human consumption demonstrated generally good to excellent water quality, proving to be unaffected by mining operations. Findings show that in arid regions, it is crucial to regularly revise environmental effects of water-intense mining activities to ensure sustainable water use and to lessen risks to nearby ecosystems and local communities. Graphical Abstract

The evaluation of raindrop size distribution (DSD) is a crucial subject in radar meteorology, as it determines the relationship between radar reflectivity (Z) and rainfall rate (R). The coefficients (a and b) of the Z-R relationship vary significantly due to several factors (e.g., climate and rainfall intensity), rendering the characterization of local DSD essential for improving radar quantitative precipitation estimation. This study used a unique network of 21 disdrometers with high spatio-temporal resolution in Mexico City to investigate changes in the local drop size distribution (DSD) resulting from seasonal fluctuations, rain rates, and topographical regions (flat urban and mountainous). The results indicate that the DSD modeling utilizing the normalized gamma distribution provides an adequate fit in Mexico City, regardless of geographical location and season. Regional variation in DSD’s slope, shape, and parameters was detected in flat urban and mountainous areas, indicating that distinct precipitation mechanisms govern rainfall in each season. Severe rain intensities (R > 20 mm/h) exhibited a more uniform and flatter DSD shape, accompanied by increased dispersion of DSD parameter values among disdrometer locations, particularly for intensities exceeding R > 60 mm/h. The coefficients a and b of the Z-R relationship exhibit significant geographic variability, dependent on the city’s topographic gradient, underscoring the necessity for regionalization of both coefficients within the metropolis.

The evaluation of raindrop-size distribution (DSD) is a crucial subject in radar meteorology, as it determines the relationship between radar reflectivity (Z) and rainfall rate (R). The coefficients (a and b) of the Z-R relationship vary significantly due to several factors (e.g., climate and rainfall intensity), rendering the characterisation of local DSD essential for improving radar quantitative precipitation estimation. This study used a unique network of 21 disdrometers with high spatio-temporal resolution in Mexico City to investigate changes in the local drop size distribution (DSD) resulting from seasonal fluctuations, rain rates, and topographical regions (flat urban, and mountainous). The results indicate that the DSD modelling utilizing the normalized gamma distribution provides an adequate fit in Mexico City, regardless of geographical location and season. Regional variation in DSD's slope, shape, and parameters was detected in flat urban and mountainous areas, indicating that distinct precipitation mechanisms govern rainfall in each season. Severe rain intensities (R > 20 mm/h) exhibited a more uniform and flatter DSD shape, accompanied by increased dispersion of DSD parameter values among disdrometer locations, particularly for intensities exceeding R > 60 mm/h. The coefficients a and b of the Z-R relationship, exhibit significant geographic variability, dependent on the city's topographic gradient, underscoring the necessity for regionalisation of both coefficients within the metropolis.

This study employs a thorough methodology to define water sustainability criteria for the development of new pig farms on the karst aquifer of Yucatan, Mexico. The integrated approach entails a field campaign to assess water quality from the aquifer (wells and cenotes) and effluents from designated pig farms to evaluate adherence to environmental regulations, alongside the utilisation of an extensive pig farm database that includes pig populations by the municipality in Yucatan. The water sustainability of pig farming in Yucatan was analysed by evaluating the nitrogen greywater footprint and water pollution levels for this municipality sector. The intensive pig farming practices in Yucatan significantly contribute to water contamination through nutrient runoff, namely nitrogen and phosphorus. Moreover, the breach of environmental regulations concerning pig farm effluents is demonstrated. This highlights the urgent need to regulate and monitor the expansion of new pig farms in Yucatan. Results introduce evidence-based criteria and their thresholds for achieving water sustainability in the pig sector at the municipal level (Pigs/ha = 1.0 and WPL < 1.1). This facilitated a concerted effort between national and state authorities to limit the proliferation of pig farms in order to safeguard the aquifer’s water quality.

This study employs a thorough methodology to define water sustainability criteria for the development of new pig farms on the karst aquifer of Yucatan, Mexico. The integrated approach entails a field campaign to assess water quality from the aquifer (wells and cenotes) and effluents from designated pig farms to evaluate adherence to environmental regulations, alongside the utilisation of an extensive pig farm database that includes pig populations by municipality in Yucatan. To analyse the water sustainability of pig farming in Yucatan, we analysed the nitrogen grey water footprint and water pollution levels for this sector by municipality. The intensive pig farming practices in Yucatan significantly contribute to water contamination through nutrient runoff, namely nitrogen and phosphorus. Moreover, the breach of environmental regulations concerning pig farm effluents is demonstrated. This highlights the urgent need to regulate and monitor the expansion of new pig farms in Yucatan. Results introduce evidence-based criteria and their thresholds for achieving water sustainability in the pig sector at the municipal level (Pigs/ha=1.0 and WPL <1.1). This facilitated a concerted effort between national and state authorities to limit the proliferation of pig farms in order to safeguard the aquifer's water quality.

En este trabajo se presenta una aplicación práctica del uso de las tecnologías de la información y comunicación (TIC) en la gestión de riesgos de desastres debidos a precipitaciones extremas en regiones urbanas. El objetivo es plantear, a partir del caso de estudio del deslizamiento del cerro del Chiquihuite, una de las formas en las que se puede aprovechar la información del Observatorio Hidrológico del Instituto de Ingeniería de la Universidad Nacional Autónoma de México (OH-IIUNAM) para mejorar la gestión de desastres generadas por precipitaciones extremas. En el caso de estudio, se utilizan los datos del OH-IIUNAM para el análisis temporal y espacial de las tormentas que se presentaron en la Zona Metropolitana del Valle de México entre el 1 y 9 de septiembre de 2021; también se considera el sismo que ocurrió el 7 de septiembre del mismo año. La conjunción de ambos fenómenos produjo un deslizamiento del cerro el 10 de septiembre de 2021, que provocó grandes daños en las viviendas y pérdidas humanas. En el análisis temporal realizado se encontró que las tormentas más importantes ocurrieron entre los días 1 y 8 de septiembre, destacando las tormentas de los días 6 y 7 en intensidad y precipitación acumulada. En cuanto al análisis espacial, se utilizó la interpolación IDW (interpolación de distancia inversa ponderada) para estimar la precipitación en toda la Ciudad de México (CDMX) en el periodo del 1 al 9 de septiembre, encontrándose que la zona del cerro del Chiquihuite fue una de las áreas donde cayó mayor cantidad de agua de lluvia.