Félix Francés

Assessing and forecasting the impacts of global change on Mediterranean rivers. The SCARCE Consolider project on Iberian basins

IntroductionThe Consolider-Ingenio 2010 project SCARCE, with the full title “Assessing and predicting effects on water quantity and quality in Iberian Rivers caused by global change” aims to examine and predict the relevance of global change on water availability, water quality, and ecosystem services in Mediterranean river basins of the Iberian Peninsula, as well as their socio-economic impacts. Starting in December 2009, it brought together a multidisciplinary team of 11 partner Spanish institutions, as well as the active involvement of water authorities, river basin managers, and other relevant agents as stakeholders.MethodsThe study areas are the Llobregat, Ebro, Jucar, and Guadalquivir river basins. These basins have been included in previous studies and projects, the majority of whom considered some of the aspects included in SCARCE but individually. Historical data will be used as a starting point of the project but also to obtain longer time series. The main added value of SCARCE project is the inclusion of scientific disciplines ranging from hydrology, geomorphology, ecology, chemistry, and ecotoxicology, to engineering, modeling, and economy, in an unprecedented effort in the Mediterranean area. The project performs data mining, field, and lab research as well as modeling and upscaling of the findings to apply them to the entire river basin.ResultsScales ranging from the laboratory to river basins are addressed with the potential to help improve river basin management. The project emphasizes, thus, linking basic research and management practices in a single framework. In fact, one of the main objectives of SCARCE is to act as a bridge between the scientific and the management and to transform research results on management keys and tools for improving the River Basin Management Plans. Here, we outline the general structure of the project and the activities conducted within the ten Work Packages of SCARCE.

Modeling the Evolution of Riparian Woodlands Facing Climate Change in Three European Rivers with Contrasting Flow Regimes

Global circulation models forecasts indicate a future temperature and rainfall pattern modification worldwide. Such phenomena will become particularly evident in Europe where climate modifications could be more severe than the average change at the global level. As such, river flow regimes are expected to change, with resultant impacts on aquatic and riparian ecosystems. Riparian woodlands are among the most endangered ecosystems on earth and provide vital services to interconnected ecosystems and human societies. However, they have not been the object of many studies designed to spatially and temporally quantify how these ecosystems will react to climate change-induced flow regimes. Our goal was to assess the effects of climate-changed flow regimes on the existing riparian vegetation of three different European flow regimes. Cases studies were selected in the light of the most common watershed alimentation modes occurring across European regions, with the objective of appraising expected alterations in the riparian elements of fluvial systems due to climate change. Riparian vegetation modeling was performed using the CASiMiR-vegetation model, which bases its computation on the fluvial disturbance of the riparian patch mosaic. Modeling results show that riparian woodlands may undergo not only at least moderate changes for all flow regimes, but also some dramatic adjustments in specific areas of particular vegetation development stages. There are circumstances in which complete annihilation is feasible. Pluvial flow regimes, like the ones in southern European rivers, are those likely to experience more pronounced changes. Furthermore, regardless of the flow regime, younger and more water-dependent individuals are expected to be the most affected by climate change.

Distributed sediment yield modelling: Importance of initial sediment conditions

Abstract The importance of initial sediment conditions on model calibration and validation is analysed. A sediment model was calibrated and validated under three different initial sediment conditions: (0) no sediment availability, (1) calibration of the initial sediment condition and (2) using a warm-up simulation. The model results were assessed in terms of the graphic of fine sediment transport, or sedigraphs, and the visual fit of the hysteresis on the sediment rating. All strategies provided adequate results. However, the loop rating curve analysis demonstrated that the choice of initial sediment conditions affected the simulation results. Without any initial sediment condition, the model results were typically inferior to the simulation results with calibration or warm-up. The calibration of initial conditions proved to be the most reliable technique to generate clockwise hysteresis loops, but failed in reproducing other loop types. Overall, the warm-up simulations showed encouraging results, providing satisfactory fine sedigraph simulation results.

Using the TCEV distribution function with systematic and non-systematic data in a regional flood frequency analysis

Abstract: Due to the social and economic implications, flood frequency analysis must be done with the highest precision. For this reason, the most suitable statistical model must be selected, and the maximum amount of information must be used. Floods in Mediterranean rivers can be produced by two different mechanisms, which forces the use of a non-traditional distribution like the TCEV. The information can be increased by using additional non-systematic data, or with a regional analysis, or both. Through the statistical gain concept, it has been shown that in most cases the use of additional non-systematic information can decrease the quantile estimation error in about 50%. In a regional analysis, the␣benefit of additional information in one station, is propagated to the rest of␣the␣stations with only a small decrease with respect to the at-site equivalent analysis.

On the Use of Unmanned Aerial Systems for Environmental Monitoring

Environmental monitoring plays a central role in diagnosing climate and management impacts on natural and agricultural systems; enhancing the understanding of hydrological processes; optimizing the allocation and distribution of water resources; and assessing, forecasting, and even preventing natural disasters. Nowadays, most monitoring and data collection systems are based upon a combination of ground-based measurements, manned airborne sensors, and satellite observations. These data are utilized in describing both small- and large-scale processes, but have spatiotemporal constraints inherent to each respective collection system. Bridging the unique spatial and temporal divides that limit current monitoring platforms is key to improving our understanding of environmental systems. In this context, Unmanned Aerial Systems (UAS) have considerable potential to radically improve environmental monitoring. UAS-mounted sensors offer an extraordinary opportunity to bridge the existing gap between field observations and traditional air- and space-borne remote sensing, by providing high spatial detail over relatively large areas in a cost-effective way and an entirely new capacity for enhanced temporal retrieval. As well as showcasing recent advances in the field, there is also a need to identify and understand the potential limitations of UAS technology. For these platforms to reach their monitoring potential, a wide spectrum of unresolved issues and application-specific challenges require focused community attention. Indeed, to leverage the full potential of UAS-based approaches, sensing technologies, measurement protocols, postprocessing techniques, retrieval algorithms, and evaluation techniques need to be harmonized. The aim of this paper is to provide an overview of the existing research and applications of UAS in natural and agricultural ecosystem monitoring in order to identify future directions, applications, developments, and challenges.

Modelling the emerging pollutant diclofenac with the GREAT-ER model: application to the Llobregat River Basin.

The present research aims at giving an insight into the increasingly important issue of water pollution due to emerging contaminants. In particular, the source and fate of the non-steroidal anti-inflammatory drug diclofenac have been analyzed at catchment scale for the Llobregat River in Catalonia (Spain). In fact, water from the Llobregat River is used to supply a significant part of the Metropolitan Area of Barcelona. At the same time, 59 wastewater treatment plants discharge into this basin. GREAT-ER model has been implemented in this basin in order to reproduce a static balance for this pollutant for two field campaigns data set. The results highlighted the ability of GREAT-ER to simulate the diclofenac concentrations in the Llobregat Catchment; however, this study also pointed out the urgent need for longer time series of observed data and a better knowledge of wastewater plants outputs and their parameterization in order to obtain more reliable results.

Incorporating Non-Systematic Information to Flood Frequency Analysis Using the Maximum Likelihood Estimation Method

Non-systematic information at a gauge station is defined as the censored information for a period prior to the systematic record. Depending on the source, we can distinguish between historical information and paleofloods. Non-systematic information can be classified according to the statistical analysis based on the type of censoring which generates it. When there is a given censoring limit, it is called censored information type 1. The value of non-censored floods may or may not be known. We will call it “censored information” (CE) when the K floods that exceeded the threshold level of perception during the non-systematic period of M length are known. If their values are unknown, it will be called “binomial censored” (BC). If there is no censoring limit, the information is called censored information type 2. In this case the K largest floods during the non-systematic period are known, K being a deterministic variable. As the largest paleoflood tends to remove the evidence left by other paleofloods, K is usually equal to 1; this information is called “maximum flood” (MF).

Introduction to Hydrology

Hydrology deals with the occurrence, movement, and storage of water in the earth system. Hydrologic science comprises understanding the underlying physical and stochastic processes involved and estimating the quantity and quality of water in the various phases and stores. The study of hydrology also includes quantifying the effects of such human interventions on the natural system at watershed, river basin, regional, country, continental, and global scales. The process of water circulating from precipitation in the atmosphere falling to the ground, traveling through a river basin (or through the entire earth system), and then evaporating back to the atmosphere is known as the hydrologic cycle. This introductory chapter includes seven subjects, namely, hydroclimatology, surface water hydrology, soil hydrology, glacier hydrology, watershed and river basin modeling, risk and uncertainty analysis, and data acquisition and information systems. The emphasis is on recent developments particularly on the role that atmospheric and climatic processes play in hydrology, the advances in hydrologic modeling of watersheds, the experiences in applying statistical concepts and laws for dealing with risk and uncertainty and the challenges encountered in dealing with nonstationarity, and the use of newer technology (particularly spaceborne sensors) for detecting and estimating the various components of the hydrologic cycle such as precipitation, soil moisture, and evapotranspiration.

Ecohydrological-Based Forest Management in Semi-arid Climate

The role of forests on the provision and regulation of non-marketed ecosystem services is well known (Thorsen et al. 2014). This is especially important in areas like the Mediterranean, where protective forests play a major role against soil erosion and degradation, landscape quality and stabilization of the hydrological cycle. Socio-economic and cultural changes affecting rural society from the 1960s have produced a demographic decline, and with it, an abandonment of rural activities, leading to an expansion and densification of forest and scrub. Forest encroachment may decrease the streamflow from upper catchments (Gallart and Llorens 2004); this study reports a decrease in average annual flow of major Spanish rivers between 37 and 59%, partly explained by the densification of upstream forests, and increasing interception loss. Moreover, some Mediterranean basins (e.g. Segura and Jucar in Spain) present very serious problems of water scarcity, because of a combination of low/irregular rainfall and high rates of evapotranspiration, that has resulted in overuse of groundwater resources (Estrela et al. 2000a, b). These problems may even endanger urban water supply (approx. 15% of the total water supply in Spain). In addition, the Mediterranean region is already suffering some significant impacts of the climate change, such as longer dry seasons, or lower soil moisture content (Giorgi and Lionello 2008; Garcia-Ruiz et al. 2011). All these issues have raised concern about the importance of forests and water interactions in the Mediterranean (Birot et al. 2011).

Exploring the key drivers of riparian woodland successional pathways across three European river reaches

Climate change and river regulation are negatively impacting riparian vegetation. To evaluate these impacts, process‐based models are preferred over data‐driven approaches. However, they require extensive knowledge about ecohydrological processes. To facilitate the implementation of such process‐based models, the key drivers of riparian woodland successional pathways across three river reaches, in Austria, Portugal, and Spain, were explored, employing two complementary approaches. The principal component analyses highlighted the importance of the physical gradients determining the placement of the succession phases within the riparian and floodplain zones. The generalized additive models revealed that the initial and pioneer succession phases, characteristic of the colonization stage, appeared in areas highly morphodynamic, close in height and distance to the water table, and with coarse substrate, whereas elder phases within the transitional and mature stages showed incremental differences, occupying less dynamic areas with finer substrate. The Austrian site fitted well the current successional theory (elder phases appearing sequentially further up and distant), but at the Portuguese site, the tolerance of the riparian species to drought and flash flood events governed their placement. Finally, at the Spanish site, the patchy distribution of the elder phases was the remnants of formative events that reshaped the river channel. These results highlight the complex relationships between flow regime, channel morphology, and riparian vegetation. The use of succession phases, which rely on the sequential evolution of riparian vegetation as a response to different drivers, may be potentially better reproducible, within numerical process‐based models, and transferable to other geographical regions.