Person: Mezger Lorenzo, Gabriel
Loading...
First Name
Gabriel
Last Name
Mezger Lorenzo
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
Department
Geodinámica, Estratigrafía y Paleontología
Area
Geodinámica Interna
Identifiers
4 results
Search Results
Now showing 1 - 4 of 4
Item Análisis de la implementación de caudales ecológicos en los ríos españoles(2023) Mezger Lorenzo, Gabriel; De Stefano, Lucía; González del Tánago, MartaLos cambios en el régimen hidrológico de los ríos como consecuencia de las actividades humanas, se consideran una de las principales amenazas para el mantenimiento de la integridad de los ecosistemas fluviales. Como respuesta a esta problemática, surgió a mediados del siglo XX el concepto de caudal ecológico. Aunque con diversas formas y definiciones, los caudales ecológicos se consideran una herramienta de gestión capaz de mitigar los impactos derivados de las alteraciones hidrológicas y cumplir así determinados objetivos ambientales. En Europa, la entrada en vigor de la Directiva Marco del Agua (DMA) en el año 2000 supuso un cambio en el paradigma de la gestión de los recursos hídricos. Desde entonces, la gestión pasó a estar orientada al objetivo de alcanzar el buen estado de las masas de agua continentales. Reconociendo los caudales ecológicos como una medida orientada a la consecución de este objetivo, numerosos países regularon e incluyeron en su legislación diferentes aspectos relativos al diseño, establecimiento y seguimiento de los caudales ecológicos...Item Analysis of the Evolution of Climatic and Hydrological Variables in the Tagus River Basin, Spain(Water, 2022) Mezger Lorenzo, Gabriel; De Stefano, Lucia; González del Tánago, MartaDuring the second half of the 20th century, several Spanish rivers experienced a decrease in the availability of water resources which coincided with an increase in human water demands. This situation is expected to be exacerbated by climate change. This study analyses the evolution of annual streamflow in 16 sub-basins of the Tagus River basin (Spain) during the 1950–2010 period and its relationship with selected variables. Our main objective is to characterize changes in in-stream flows and to identify what factors could have contributed to them. First, we used non-parametric tests to detect trends in the hydro-climatic series. Then, we analyzed changes in the runoff coefficient and applied regression-based techniques to detect anthropic drivers that could have influenced the observed trends. The analysis revealed a general decreasing trend in streamflow and an increasing trend in air temperature, while trends in precipitation are less clear. Residuals from regression models indicate that the evolution of several non-climatic factors is likely to have influenced the decline in streamflow. Our results suggest that the combination of the expansion of forested areas (a 60% increase from 1950 to 2010) and irrigated land (a 400% increase since 1950) could have played an important role in the reduction of streamflow in the Tagus basin.Item Assessing the Establishment and Implementation of Environmental Flows in Spain(Environmental Management, 2019) Mezger Lorenzo, Gabriel; De Stefano, Lucia; González del Tánago, MartaThe alteration of natural flows due to water withdrawals and the presence of hydraulic infrastructure poses significant threats to the integrity of riverine ecosystems. The establishment of environmental flows (EF) has been conceived as a water management tool to mitigate the impact of in-stream flows alteration. To date, a large body of literature has focused on methods to define EF, but less attention has been paid to documenting and assessing their actual implementation on the ground. This article provides a framework to describe and assess the process of design, application, and monitoring of EF at a river basin level. The framework is applied to Spain, where significant efforts have been made during the past decade to define and implement EF across the country. The goal of the paper is to identify strengths and opportunities for improving the implementation of EF at country level. The Spanish legislation establishes that EF should contribute to the achievement of the good ecological status of surface water bodies as required by the European Union Water Framework Directive. Several pitfalls in the design, application, and monitoring of this important river management measure constrain the ability of the existing EF to deliver that fundamental outcome.Item Environmental flows and the mitigation of hydrological alteration downstream from dams: The Spanish case(Journal of Hydrology, 2020) Mezger Lorenzo, Gabriel; González del Tánago, Marta; De Stefano, LuciaDams cause significant alteration in natural flow patterns of rivers throughout the world. As a response, many countries have established environmental flows (e-flows) to reduce hydrological alteration and mitigate ecosystem degradation. This paper assesses hydrological changes downstream from dams in 22 rivers in Spain, 12 of them located in northern wetter regions (Duero and Ebro basins) and the remaining 10 in southern drier regions (Guadalquivir and Júcar basins). First we compared pre-dam and post-dam instream flow patterns, and then we considered a third period starting with the implementation of e-flows. We quantified changes in mean annual flows, monthly flows, and magnitude and timing of extreme flows (1-day maximum, 95th percentile, 1-day minimum and 5th percentile). The analysis aimed at: i) characterizing hydrological alteration in regulated rivers in four river basins in Spain, with a special focus on differences across regions; and (ii) assessing the capacity of the implemented e-flows to mitigate flow regime alteration downstream from dams. All the studied rivers displayed significant changes in magnitude and timing of flows after the dam construction. A quite homogenous trend was observed in the drier basins, where mean annual flows and annual extreme flows decreased significantly. The wetter basins showed no uniform patterns in mean annual flows, while 1-day maximum and 95th percentile flow values decreased. In contrast to drier basins, 1-day minimum and 5th percentile flow values increased markedly. In most cases, the natural Mediterranean annual hydrograph was inverted, with the high-flow period occurring during the low precipitation months (summer) and the low-flow period during the wet season. After e-flows implementation, these patterns of hydrological alteration remained almost unchanged, pointing to a limited capacity of current e-flows to mitigate the hydrological impacts downstream from dams.