Most Latin American glaciers are located in the tropical Andes. The melting processes of Glacier "15" on Antisana volcano were studied to understand the relationship between glacier retreat and natural climate variability and global climate change. Glaciers on the Antisana volcano are crucial sources of water as they feed the headwater rivers that supply Quito with potable water. The aim of this study was to build empirical models based on multiple correlations to reconstruct the mass loss of glaciers over a period of 10 years at three scales: local (data recorded by meteorological stations located around the volcano), regional (data from stations located around the country) and global (re-analysis data). Data quality was checked using graphical and statistical methods. Several empirical models based on multiple correlations were created to generate longer time series (42 and 115 years) of the mass balance for the glacier ablation zone. The long mass balance series were compared with the temperature variation series of the Earth's surface in the Southern Hemisphere to estimate the relation between the mass balance and global warming. Our results suggest that the meteorological factors that best correlate with mass balance are temperature and wind.Key words Ecuador; Andes; Antisana volcano; glacier; ablation zone mass balance; empirical models Modélisation empirique du bilan de masse des glaciers tropicaux d'Amérique du Sud: cas du volcan Antisana, Equateur Résumé La plupart des glaciers d'Amérique latine sont situées dans les Andes tropicales. Les processus de fusion du glacier « 15 » sur le volcan Antisana ont été étudiés pour comprendre la relation entre le recul des glaciers et la variabilité naturelle du climat et / ou le changement climatique mondial. Les glaciers situés sur le volcan Antisana sont des ressources en eau essentielles car ils alimentent les rivières qui fournissent l'eau potable de Quito. L'objectif de cette étude était de construire des modèles empiriques sur la base de corrélations multiples afin de reconstituer la perte de masse des glaciers sur une période de dix ans à trois échelles : locale (données enregistrées par les stations météorologiques situées autour du volcan), régionales (données provenant de stations situées dans le pays) et mondiale (données de réanalyse). La qualité des données a été vérifiée à l'aide de méthodes graphiques et statistiques. Plusieurs modèles empiriques basés sur les corrélations multiples ont été créés pour générer des séries plus longues (42 et 115 ans) du bilan de masse de la zone d'ablation du glacier. La longue série de bilans de masse a été comparée à la courbe de variation de la température de surface de la Terre dans l'hémisphère Sud pour estimer la relation entre le bilan de masse et le réchauffement climatique. Nos résultats suggèrent que les facteurs météorologiques présentant la meilleure corrélation avec le bilan de masse sont la température et le vent.
Changes in flood loads and reservoir levels, produced by climate change (CC), represent an increasing concern for dam safety managers and downstream populations, highlighting the need to define adaptation strategies based on the dam failure risk management framework. Currently, thousands of dams worldwide, varying in use, age, and maintenance, may represent a threat to downstream cities in the case of structural failure. Several studies relate the failure of dams to several issues in the spillway, which may be even more vulnerable in CC conditions. This study provides a review of dam safety threats due to CC and approaches for the design/redesign of the spillway to cope with CC. A general four-stage methodology is proposed: data gathering and hydro-climatic, hydrological, and hydraulic analyses. Afterward, this methodology is applied to the spillway design for the Sube y Baja dam in Ecuador. The Probable Maximum Precipitation (PMP) increases around 20% considering CC under the Representative Concentration Pathway 8.5. Such an increment derived a 25% increase in the spillway maximum flow. These results show that the non-stationary hydrological regimes related to CC require a revision of engineering design criteria for hydraulic structures in general, and call for a consensus on design variables under CC.
Hydrogeology in the Andes cordillera reflects its complex geological history. In most cases, groundwater flows through fractures and faults that compartmentalize the volcanic material, and through the primary porosity of the volcano-sedimentary material. The volcanic mineral context and geothermal environment mark the groundwater chemistry, especially in the high concentrations of specific trace elements. This study focuses on the complex system of the Tumbaco – Cumbayá – Los Chillos aquifer, in the vicinity of the Ilaló volcano near Quito (Ecuador). Hydrodynamic, geochemical and isotopic tools were used to assess the chemical characteristics of water and its origin, identify the recharge areas, and estimate the transit time of water using simple methods and scarce data. Results revealed two distinct aquifers, one in the volcanic cone located in the center of the study area, and the other in the volcano-sedimentary series of the Tumbaco – Cumbayá – Los Chillos valley. The volcanic aquifer is characterized by a high mineralization, a recharge zone between 2400 m asl and 3100 m asl, and radiocarbon concentrations lower than 20 pmc. The volcano-sedimentary aquifer seems to behave as a partly disconnected system, between the north and the south of Ilaló volcano, and also with a great heterogeneity, maybe due to the presence of lenses of volcanic ash. It has an intermediate mineralization, a mean recharge zone between 2,300 and 2,700 m asl, and 14C activities between 45.4 and 87.4 pmc in apparent contradiction with the hydrodynamic mass balance.
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