Valley Of Mexico Research Articles

Late Miocene NE-SW strike-slip fault system of the Mexico basin, central Trans-Mexican Volcanic Belt: Origin, deformation, and reactivation

A NE-SW fault system, observed in the northeast portion of the eastern sector of the Trans-Mexican Volcanic Belt, has been active since the Pliocene-Holocene time with dip-slip kinematics. These NE-SW faults belong to the Tenochtitlan fault system that extends from the southwest coast of Mexico to the NE zone of the Mexico basin. The length of this fault system suggests a complex deformation history, which is unknown before the Pliocene. In addition, the kinematics of the NE-SW faults and the tectonic conditions are unknown before their current activity. In this study, we investigate the geometry and kinematics of the NE-SW faults in the Miocene rocks in the central part of the Mexico basin (Guadalupe Range) for to know the kinematics of these faults during the Late Miocene time. Our results suggest that the Miocene rocks record two deformation events, one event is related to crustal shortening which produced a strike-slip activity in the NE-SW faults during the Late Miocene. The second deformation event is associated with crustal extension and the activity of the NE-SW faults with dip-slip kinematics. This extensional event was active during the Pliocene-Holocene. The re-activation analysis and our observations in the Guadalupe Range suggests that the NE-SW normal faults in the Tizayuca-Chignahuapan region are the product of the re-activation of previous NE-SW strike-slip faults. The change in the kinematics of the NE-SW faults explains the complex geometry of the damage zone and the high amount of the geological fractures in the Miocene rocks of the Mexico Basin. The activity type of the NE-SW faults is probably related to the dynamic of the subduction process in the southwest of Mexico, associated with the change in the inclination (decrease) and the convergence velocity of the Cocos Plate.

Diatom evidence for a groundwater divide that limited the extent of Lake Estancia, New Mexico, USA, highstands during the Last Glacial Maximum

Abstract A high-resolution time series of diatoms from the Estancia Basin of central New Mexico, USA, reveals decadal to millennial changes in water chemistry during the Last Glacial Maximum (LGM) and suggests that groundwater leakage limited the size of Lake Estancia highstands. Previous work showed that the lake expanded at least five times during the LGM, with each highstand reaching the same elevation; numerical modeling experiments showed that highstands required increases in precipitation of 1.5–2 times that of modern times but also demonstrated that these conditions could have lasted for only a few decades or the lake would have overflowed the basin’s sill. The fact that the lake returned to the same elevation suggests that highstands were climatologically similar. Here we present an alternative scenario, that once the lake reached a particular threshold volume, groundwater leakage prevented further expansion, which means that precipitation increases may have been larger than previously thought. The LGM diatom sequence is dominated by freshwater planktonic species in the Lindavia ocellata complex, the freshwater to brackish littoral species Pseudostaurosira brevistriata, and the brackish to saline benthic species Diploneis cf. smithii, all of which show decadal to centennial oscillations that were likely driven by solar cycles. Canonical correspondence analyses using mineralogical time series as proxies for wetter and drier conditions reveal that diatom assemblages varied with salinity and pH/alkalinity and suggest that groundwater outflow led to variable water chemistry for different highstands of the same magnitude. Nonmetric multidimensional scaling confirms the uniqueness of each highstand in terms of the diatom assemblages. The diatom data presented here are among only a handful of such records for Pleistocene pluvial lakes in the American West and reveal that saline alkaline lakes can yield important information despite valve preservation issues.

A Unified Hydrogeological Conceptual Model of the Mexico Basin Aquifer after a Century of Groundwater Exploitation

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.

Effects of Urbanization on Extreme Climate Indices in the Valley of Mexico Basin

This study analyzes 50 annual climate change indices related to temperature and precipitation in the Valley of Mexico basin for the period 1951–2010. First, a quality and homogenization analysis of 90 weather stations (categorized as urban, suburban, and rural) in the basin was performed using the Climatol algorithm. The non-parametric Mann–Kendall test and the Sen’s slope method were applied to determine the existence of a trend and to estimate the magnitude of the change in extreme climate indices, respectively. To eliminate the serial correlation problem, the lag-1 method and the Patakamuri tests were used. Statistically significant positive trends were found for SU, TMm, TNm, TNn, TX90p, and WSDI, as well as negative ones for FD, TX10p, TN10p, CSDI, and HDDheat18. The results seem to support an influence of anthropogenic global warming on the study region, rather than local effects of urbanization. However, it is likely that some significant differences in the urban change rate of some indices could be due to local effects, such as the difference in land cover that occurs between urban and rural stations. Not enough statistically significant results were found for the climate change indices related to precipitation in most of the stations. Compared to other studies in the Mexico City area, the main contribution of this study is the analysis of 50 climate indices in a 60-year period working with a quality-controlled and homogenized database.

Identification of fossil contourite drifts in the Delaware Basin, U.S.A.

ABSTRACT Carbonate contourite drifts formed by bottom currents are common on modern sea floors but are rarely defined in the rock record. Regional subsurface well-log mapping in the northern Delaware Basin in southeast New Mexico, USA, reveals early Permian carbonate-dominated elongate, mounded accumulations along the slope of the western margin of the basin. Thickness maps also show possible moats oriented oblique to depositional dip. The thickness variations and moat geometries are hard to explain by deposition from gravity flows but are consistent with deposition from bottom currents with a counterclockwise deflection in the basin. The contourite drift system consists of three large elongate carbonate drifts that form in relation to significant bathymetric irregularities which may alter currents, resulting in localized drift accumulations along the slopes. These findings highlight the significant role bottom currents play in shaping carbonate margin and slope architecture, rivaling the impact of gravity flows. Furthermore, full-scale assessment of the basin geometry and deposits provide insight into paleo-oceanographic circulation that is inherently difficult to assess. Identification of these large sedimentary bodies requires extensive basin-wide data sets, which were acquired by decades of work in the Permian Basin, as well as comparison with drifts in modern carbonate settings. These new interpretations in one of the most data-rich geologic regions in the world indicate that drift systems may be easily overlooked and are likely more common in the ancient rock record than currently recognized.

Structural and ultrastructural injuries in leaves of Baccharis conferta and Buddleja cordata broad-leaved species of a forest impacted with ozone

The present study showed evidence of ozone damage to the structure of leaves of Baccharis conferta HBK and Buddleja cordata HBK broad-leaved species of the southwest of the Valley of Mexico using light, transmission, and scanning electron microscopy. These species are growing in the forests of Mexico City Metropolitan Area, one of the most polluted regions in the world for ozone. Ozone in the plants causes damage to the leaves and intensifies the decline of the forest at high altitudes such as the mountains where Desierto de los Leones, a National Park (DLNP), as treatment, compared with the forest of Miguel Hidalgo National Park (NINR), as control, exposed to low levels of air pollution. The most notorious damages were in the mesophyll, vascular bundle, and epidermis of the species studied in DLNP. Also the ultrastructure showed gradual injuries at the cellular level, initially higher in the vacuoles and chloroplasts and smaller in cytoplasm and mitochondria. NINR studies showed no evidence of damage in either of the two selected species or in the different microscopic techniques, which are related to measurements of low levels of air pollution.

Numerical Analysis of the Groundwater Flow System and Heat Transport for Sustainable Water Management in a Regional Semi-Arid Basin in Central Mexico

The Independence Basin is located in a semi-arid region of Mexico, delimited predominantly by volcanic mountains. Around 30 m3/s of water are extracted from regional aquifers mainly for agro-export activities, causing declines in the water table of up to 10 m/a, increased temperature and dissolved elements that are harmful to health and the environment. Regional groundwater coupled flow and heat transport under current conditions were studied on a basin-wide scale (7000 km2) using a three-dimensional finite-element model under steady-state conditions to provide support for water management decisions and transient modeling. Isothermal, forced and free thermal convection under existing hydrological conditions prior to pumping are analyzed. The results show that the interaction of topography-driven groundwater flow and buoyancy-driven free thermal convection are consistent with historical hydrological records, the characteristics of the water table, and thermal anomalies observed in the basin. The simulated groundwater recharge is near 7 ± 0.25 m3/s, a balance broken since the 1980s by extensive pumping. The results show the importance of considering the groundwater temperature, its transient response in the evolution of groundwater extraction, and the upward migration of a thermal front through the fractured aquifer that has increased risks for health and sustainability.

Water Diversion in the Valley of Mexico Basin: An Environmental Transformation That Caused the Desiccation of Lake Texcoco

Mexico’s basin is one of the most altered in the country, owing to the presence of the megalopolis of Mexico City. Lake Texcoco, which had the basin’s biggest extension, dried up almost completely. The basin’s evolution over time led in the formation of a megabasin in which water is transported from one source to another to serve the urban region and subsequently drained to prevent flooding. The major hydrotechnical works in Mexico Basin have been interpreted as a solution to the problem of flooding in Mexico City, but they were actually part of a much larger strategy of territorial appropriation by the Spanish colonists. The ecological imbalance that has resulted has sparked a variety of social issues. For the purpose of analyzing the environmental transformation of Lake Texcoco over the last 500 years, actors and processes that influenced specific moments in the country’s history were identified; these elements showed the inexorable relationship between the lake and Mexico City. Subsequently, they were grouped by periods with similar trends in terms of the way in which society relates to and appropriates the natural environment of the lake. It was found that the critical moment for the desiccation of Lake Texcoco occurred during the Spanish colonial historical period as part of the redesign of the city; from then on, the same environmental imaginary prevailed century after century, shaped by social and economic factors. This study contributes to the literature on how urbanization affects natural resources by making an original theoretical contribution through an analysis based on political ecology, and it adds to the literature on how people use the prevailing federal area of the lake.

Comparative Thermodynamic Analysis of the Performance of an Organic Rankine Cycle Using Different Working Fluids

Today, the study of thermal systems that take advantage of residual thermal sources in the power generation sector is of great importance to mitigate environmental impact and promote sustainable alternatives in this sector. Among these alternatives, the organic Rankine cycle (ORC) is of great relevance since it allows taking advantage of residual energy sources at low temperatures. This work presents a methodology to evaluate the feasibility of using a refrigerant as a working fluid in an organic Rankine cycle based on an exergetic viability index. As a case study, R134a, R600a, R245fa, and R123 refrigerants were considered. A residual thermal source was used that came from the Hybrid Cycle Plant of the Valley of Mexico. Thermodynamic analysis was performed to determine generated power, thermal efficiency, refrigerant mass flow, pinch point temperature difference, specific steam consumption, unused thermal exergy flow, exergy efficiency, and total heat transfer requirement. The weighted average of the differences between these indicators, the global warming index, and the ozone depletion potential relative to the most favorable indicator corresponded to the definition of the exergetic viability index of the refrigerant. The results indicate that the ORC operating at condensing temperatures of 25, 35, and 45 °C with R245fa shows the highest rate of exergetic viability despite not generating the greatest amount of power and being one of the refrigerants with the highest total heat transfer requirement. Finally, at condensing temperatures above 45 °C, it is observed that R600a is exergetically the most viable refrigerant used in the ORC.

Economic disparities in pollution-related mortality in three municipalities of the Metropolitan Area of the Valley of Mexico

This study explored the nature of health risks in the population of three municipalities within the Metropolitan Area of the Valley of Mexico (MAVM) by means of an empirical analysis of health effects associated with air pollution and temperature variation. Based on the environmental justice theory, we asked whether, in unequal socioeconomic municipalities of the MAVM, the association between PM10 concentrations and mortality depends on socioeconomic disparities. We differ from previous studies that have established a relationship between PM10 and mortality based on a state-space model instead of the Poisson regression model. The state-space model allows estimating the size of the unobserved at-risk population, its hazard rate, the life expectancy of individuals in that population, and the effect of changes in environmental conditions on that life expectancy. Our results show a lower hazard rate in a wealthy municipality, as compared to a higher hazard rate in a poor one. The lower hazard rate of the wealthy municipality extends life expectancy and enhances the likelihood of inhabitants staying long-lasting within the population at risk, thus increasing the size of that population, as compared to the population at risk in the poor municipality, whose members show a lower life expectancy. Thus, the smaller the at-risk population, the sicker its average member and the smaller the impact on long-term mortality. Our study examines how regional health disparities could provide information for public health policy initiatives which might improve living conditions among different communities.

Hydraulic Opulence: Artesian Wells and bathing in Mexico, 1850–1900

Before 1850 Mexico City’s scarce water resources were produced by a handful of nearby springs channeled through centuries-old city infrastructures to a limited number of taps in large houses and to public fountains that served the majority of the population. In the second half of the nineteenth century, artesian wells tapping the Valley of Mexico’s aquifers enabled landowners and businessmen to produce copious amounts of water almost anywhere with little effort. Private access to groundwater supplied newly built bathhouses and propelled changes to, and the rapid expansion of, social practices of bathing and swimming. This infrastructure, expanded supply, and new practices gave shape to a widely shared and historically durable assumption that there are no limits to the supply of water – what I call hydraulic opulence. After 1900 hydraulic opulence fueled soaring demand and continuous efforts by the state to expand hydraulic infrastructure and supply.

The impact of tropical cyclones on potential offshore wind farms

The climate crisis has led to an increased interest in renewable energy, and in wind energy in particular. Wind farms with the largest generating potential are generally located offshore. In this study we consider the case of Mexico, a sub-tropical country in North-America. Due to Mexico's location, offshore wind farms (OWF) would be at risk of damage from strong winds associated with tropical cyclones (TCs) in both the Pacific and the Gulf of Mexico basins. Thus, here we ask whether there are any regions in Mexico combining a high generating potential and a low risk from tropical cyclones. To answer this question, the ERA5 reanalysis has been used to identify two sites on the Pacific coast and two sites in the Gulf of Mexico with high wind power potential. Then, using the ERA5 reanalysis and TC best-track observational data, the potential effects of four major hurricanes and the climatological hazard posed by TC-related damaging winds on OWFs at those sites have been investigated. The return period for TCs with near-surface winds exceeding 50m s−1, a threshold associated with increased structural damage likelihood, has been estimated at as low as 8 years for the Gulf of Mexico and above 64 years for Pacific coast. Therefore, in terms of the magnitude of the TC-related hazard, the Pacific coast sites are found to be preferred as locations for the development of OWFs. These results are relevant for any planning of offshore wind energy in Mexico, and the methodology applicable to any other sub-tropical region in which the risk of tropical cyclones is present.

Coupled effects of observation and parameter uncertainty on urban groundwater infrastructure decisions

Abstract. Urban groundwater management requires complex environmental models to represent interactions between hydrogeological processes and infrastructure systems. While the impacts of external uncertainties, such as climate and population growth, have been widely studied, there is limited understanding of how decision support is altered by endogenous uncertainties arising from model parameters and observations used for calibration. This study investigates (1) the importance of observation choice and parameter values on aquifer management objectives when controlling for model error and (2) how the relative performance of management alternatives varies when exposed to endogenous uncertainties, both individually and in combination. We use a spatially distributed groundwater model of the Valley of Mexico, where aquifer management alternatives include demand management, targeted infiltration, and wastewater reuse. The effects of uncertainty are evaluated using global sensitivity analysis, performance ranking of alternatives under a range of human–natural parameters, and identification of behavioral parameter sets filtered with an error metric calculated from varying subsets of observations. Results show that the parameters governing hydraulic conductivity and total water use in the basin have the greatest effect on management objectives. Error metrics (i.e., squared residuals of piezometric head) are not necessarily controlled by the same parameters as the head-based objectives needed for decision-making. Additionally, observational and parameter uncertainty each play a larger role in objective variation than the management alternatives themselves. Finally, coupled endogenous uncertainties have amplifying effects on decision-making, leading to larger variations in the ranking of management alternatives than each on their own. This study highlights how the uncertain parameters of a physically based model and their interactions with uncertain observations can affect water supply planning decisions in densely populated urban areas.

An ostracod-based record of paleoecological conditions during MIS6 and MIS5, from Lake Chalco, Basin of Mexico

An ostracod-based record of paleoecological conditions during MIS6 and MIS5, from Lake Chalco, Basin of Mexico

Significance of U-Pb detrital zircon geochronology for mudstone provenance

AbstractDetrital zircon U-Pb studies of mudstone provenance are rare but may preferentially fingerprint distal zircon sources. To examine this issue, Pierre Shale and Trinidad Sandstone deposited in a Late Cretaceous deltaic environment in the Raton Basin, Colorado (USA), were measured for detrital zircon U-Pb age by laser ablation–inductively coupled plasma–mass spectrometry. Two major detrital zircon age peaks at ca. 70 and 1690 Ma are found in both Pierre Shale and Trinidad Sandstone but in inversely varying proportions: 68% and 16%, respectively, for the finest zircon fraction (~15–35 μm) in the shale, and 25% and 32%, respectively, for the coarsest zircon fraction (~60–80 μm) in the sandstone. Proximal sources in the Sangre de Cristo Mountains, directly west of the Raton Basin, contain coarse-grained, ca. 1690 Ma zircon, whereas distal sources in Laramide uplifts and basins in Colorado, New Mexico, and Arizona contain fine-grained, ca. 70 Ma zircon. The results indicate that U-Pb zircon provenance of mudstone reflects availability of volcanic and other fine-grained source rocks rather than simply distal sources. U-Pb zircon provenance studies should routinely include mudstone units because these units may identify fine-grained zircon sources more reliably than sandstones alone.

Variability in mentum deformities of Tanytarsus larvae (Diptera, Chironomidae) in a metal rich basin in Northern Mexico

Mentum deformities in chironomids have been commonly used as indicators of metal contamination in freshwater ecosystems. Incidence of these deformities suggests sublethal effects and can provide early signals of environmental deterioration. While anthropogenic metal pollution is known to lead to an increase in deformities in chironomids, natural background deformity incidence information is key to their effective use as biomonitoring tools. Here we explore the incidence of deformities from 5000 Tanytarsus (Diptera, Chironomidae) menta in relation to water physicochemical, and sediment metal (Al, As, Cu, Fe, Mn, Pb, Zn) concentration data from numerous sites in the naturally metal-rich Sonora River (NW Mexico) obtained over a two-year period. Higher metal concentrations were found in the upper basin. Higher salinity, total suspended solids and conductivity were found in the lower basin. Only As and Cu were occasionally found above published threshold effect levels (TEL). The proportion of deformities (% D) was low (2.1%) and a generalized linear model only explained 25.36% of % D variability among samples; this model included several physicochemical parameters. The only metal significantly related to deformities was Cu. Despite significant spatial and temporal variability in all metal concentrations and other physicochemical parameters in the basin, we were unable to explain a strong relationship between metal concentration and deformity incidence. Our results, based on consistent % D quantification from 5000 samples from a single taxon, suggest that natural variation in metal concentrations, even when statistically significant, is not associated with notable variations in the incidence of deformities.

Enhanced oil recovery with D-Limonene diluted in brine

D-Limonene, a compound consisting of terpenes in its dextrogyrous form, is commonly used as a degreaser, hydrocarbon waste cleaner and as a sand oil separator. In this work, the use of this chemical is proposed as an alternative for enhanced oil recovery (EOR). Two oils from the southeast basin of Mexico (one medium and one extra-heavy oil) were tested for viscosity reduction with D-Limonene. The viscosity of the heavier oil @25 °C is 117,000 cP. The addition of 5% D-Limonene decreased the viscosity to 55,000 cP at same conditions, which corresponds to 53% reduction. The addition of D-Limonene also reduced the percentage of asphaltenes and paraffins in oil and increased the percentage of aromatics and resins (according to SARA analysis). D-Limonene was diluted (3% v/v) in brine and EOR tests were performed on a bioclastic sandstone rock with the medium oil. The rock has a helium permeability of 2.6 mD, slightly higher than the carbonated rocks, both characteristic of the Mexican Republic. The rock was characterized by scanning electron microscopy (SEM), porosimetry and X-ray diffraction. Contact angles were measured to know the humectability of rock with respect to oil, brine and D-Limonene. Coreflooding tests were carried out in a CoreFlood equipment at 50 °C and an average of 62.6% oil recovery with 3% D-Limonene diluted in brine was achieved. It should be noted that D-Limonene is a biodegradable and harmless product. • Oil recovery achieved with 3% D-Limonene diluted in brine was 62.6%. • Oil recovery achieved resembles other works using solvents, nanoparticles, or other chemicals with different toxicity • TD-Limonene is a biodegradable, environmentally friendly and harmless alternative product to the actual techniques of EOR

STUDY OF THE DYNAMIC BEHAVIOR OF FINE SOIL REINFORCED WITH RECYCLED POLYETHYLENE TEREPHTHALATE (PET) FIBER

ABSTRACT: PET occupies a preponderant place in plastic waste in Mexico, in the last six years the post-consumer stockpiling of PET has been the highest in America and during 2017 its recovery increased by 20,000 tons per year, their increase reached 445,000 tons per year [1]. In this way, one of the alternatives to recycling PET is produce fibers to reinforce fine soils of low shear strength and high deformation like Mexico’s city soil. For this particular case, Mexico City’s soil is notorious for its high plasticity, low strength, high compressibility and cracking tendency. Due to these, the strongest earthquakes have shown the brutal amplification and the substantial increase in the duration of the movements. In order to seek new alternatives for soil improvement in the Valley of Mexico, this study investigates the dynamic behavior of a high plasticity silty soil extracted from the former Texcoco Lake, reinforced with different PET fiber contents. The results indicate that there is a significant modification in the dynamic parameters of the soil due to fiber inclusion, an increase in the maximum elastic shear stiffness of the soil and a significant decrease in deformation for a fiber content of 0.3% at all confining pressures, this can be useful in the construction by improving the properties of this type of soil for geotechnical works through the inclusion of synthetic fibers, the large-scale use of stone materials from loan banks for stabilizing soil can be reduced, which will also avoid requiring reinforcement geosynthetics made of new materials. According to the results obtained in this research it was developed some applications and a general construction method for geotechnical works Key Words: Fiber-reinforcement, Soil stabilization, Seismic engineering, Unsaturated soils, Geosynthetics.

Impacts of Climate Change on the Water Sector in Mexico

Climate and the water cycle are intimately related; so, any change in temperatures and precipitation patterns estimated for different climate change scenarios will have an impact on the availability of water resources. The objective of this study is to present a set of regional temperature and rainfall projections for Mexico under the IPCC's AR6 climate change scenarios and estimating the possible impacts of climate change on Mexico's water resources. A set of regional temperature and rainfall projections for Mexico under the IPCC's AR6 climate change scenarios during the present century were generated by the Climate Change Knowledge Portal (CCKP) of the World Bank and together with the projections of soil moisture, Normalized Difference Vegetation Index (NVDI), Standardized Precipitation Evapotranspiration Indices (SPEI) and droughts will be evaluated. The vulnerability of Mexico's water resources. The regional models for Mexico under the IPCC AR6 climate change scenarios show temperature increases ranging from 0.5 to 5 °C, while the % change in rainfall will range from -20.3% to 13.5% depending on the scenario and analysis period. Low soil moisture (mm), negative changes in NDVI and SPEI 12 show that the North, West and Bajío areas presented reductions in precipitation and increase in temperature that caused a severe deficit of soil moisture and water stress in plants considering these areas with scarce vegetation and presence of semi-permanent meteorological drought. Under these scenarios it is expected that practically the entire country will be subjected to moderate droughts (Central and South) to extremely strong (North) that will last and sharpen between now and the end of the century. These conditions have already been registered in the main hydrological basins of Mexico and if adaptation and mitigation measures are not adopted, the availability of water is put at risk and with it the food security of the country. Also, in addition to the decrease in rainfall, it is estimated that they are more intense with the presence of extreme events, which will increase the vulnerability of some basins throughout the country, in the Central and Northern areas with extreme drought events, while in the Southeast with floods. Both scenarios would put at risk the availability of water both in quality and quantity throughout the country. To reduce the effects of climate change on water resources in Mexico, it is necessary to design and prioritize adaptation actions and implement mitigation measures that avoid intensifying the effects of climate change in the most vulnerable hydrological regions of the country.

Potential Influence of the Atlantic Multidecadal Oscillation in the Recent Climate of a Small Basin in Central Mexico

One of the main current challenges is detecting changes in the climate at the regional level. The present study tried to address this issue by looking for some influence of large-scale climate oscillations on the climate of a small and complex topography basin in Central Mexico. We collected temperature and precipitation data from 44 climate stations within an area of up to 20 km around the Apatlaco River sub-basin (~30 km south of Mexico City) during the period 1950–2013. Posteriorly, quality analysis and homogenization of the climate databases were performed by using the Climatol algorithm. We analyzed the trend of five ETCCDI climate indices through several statistical tests. Finally, we calculated simple Pearson correlations of those indices with four climate oscillation indices that have affected Mexico’s climate in the recent past. The results revealed that the Atlantic Multidecadal Oscillation had a clear influence on four of the five indices analyzed in the study area. The summer days and the extreme maximum and minimum temperatures accounted for a small increase in the temperature of the middle east (urban) basin compared to the middle west (rural), which could be a manifestation of the heat island effect or the difference in soil type (and therefore albedo) of the two zones. As expected, the midsummer drought effect predominated in most of the sub-basin, with only the uppermost part showing monsoon-type precipitation during a typical year.