Alicia Garcia-Arias

Calibration of distributed hydrological models needs to include spatial information of the hydrological processes in order to guarantee a robust spatial representation of the model state variables. Satellite remote sensing monitoring the Earth in a temporal and spatial comprehensive way stands out as a valuable resource of this kind of information. Surface soil moisture (SSM) plays a key role in the description of the hydrological cycle, especially in semi-arid areas. Nevertheless, the coarse resolution of available SSM products has restricted the use of SSM in the calibration of hydrological models to only the temporal approach. The current operational SSM estimates (1km) resulting from new sensor estimates or the application of downscaling methodologies pave the way for this spatial calibration approach. The present study explores the applicability of these spatially enhanced SSM estimates for distributed eco-hydrological modelling in Mediterranean forest basins. On one hand, it contributes to fill the existing research gap on the use of remote sensing SSM spatial patterns within the distributed hydrological modelling framework, in particular in medium/small basins. On the other hand, it serves as an indirect validation method for the spatial performance of satellite SSM products. TETIS eco-hydrological distributed model was implemented in three case studies, named Carraixet (eastern Spain), Hozgarganta (southern Spain), and Ceira (western Portugal), which were strategically selected to perform this research in the Mediterranean Region. The SSM estimates selected for evaluation were: Sentinel-1 SSM provided by the Copernicus Global Land Services (CGLS), SMAP SSM disaggregated using Sentinel-1 provided by the National Aeronautics and Space Administration (NASA), SMOS SSM provided by the Barcelona Expert Center (BEC), and SMOS and SMAP SSM disaggregated using the Dispatch algorithm provided by Lobelia Earth. The methodology employed involved a multi-objective and multi-variable calibration using the considering remote sensing SSM spatial patterns and in-situ streamflow, using the Spatial Efficiency Metric (SPAEF) and the Nash-Sutcliffe efficiency index (NSE) respectively. In spite of the spatial and temporal differences amongst products, the multi-objective calibration approach proposed increased the robustness of the hydrological modelling. Spatial and temporal agreement depends on the selection of the SSM product. The disaggregating methodology determined the spatial agreement to a greater degree than the sensor itself.

Usually, megacities expand without proper planning in a context of demographic growth and are increasingly dependent on the natural resources related to the occupied area. This is a major challenge for the sustainable management of these territories, justifying the need for a better knowledge of land use/land cover (LULC) distribution and characteristics to observe spatial anthropogenic dynamics. In this study, the Bogotá river basin and the Bogotá megacity were analyzed as a case study. The main objective of this work was to analyze the historical LULC dynamics from 1985 to 2014. Reliable forecasting scenarios were developed using the Land Change Modeler to support sustainable management and planning. Results show an expansion of the Bogotá megacity toward the Northeast and an increase of urban areas within the basin. These changes implied a loss of 58% of forest surface, a strategic ecosystem, from 1985 to 2014. This dynamic is expected to continue, with a 50% increase of urban areas between 2012 to 2050, thus the megacity and neighbor cities potentially become an “urban continuum”. A replacement of crop and pasture lands near the city is expected, even though Bogotá lands are among the best agricultural lands in the Andean region of Colombia.

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.

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.

Riparian ecosystems are required to be preserved to achieve a good ecological status. The Water Framework Directive (2000/60/EC) specifically supports the assessment of new management tools that allow the European Member States to achieve good ecological status of river‐related ecosystems. Within several approaches, a dynamic riparian vegetation distributed model (CASiMiR‐vegetation), with a time step of 1 year, has been selected as a useful first‐step tool to achieve the Water Framework Directive requirements. The model has been implemented into three river reaches with different climatic and hydrologic settings, located in three European countries. Common bases were established in the model setup. The model was calibrated independently in the Kleblach reach (Drau River, Austria), the Ribeira reach (Odelouca River, Portugal), and the Terde reach (Mijares River, Spain) with simulation periods of 8, 11 and 41 years, respectively. The parameter values and the results were comparable between the different countries. The calibration performance achieved high correctly classified instances (60%). Additionally, weighted kappa values ranged from 0·52 to 0·66 in distinguishing riparian succession phases. The model behaved similarly in the validation, even offering better results in most cases. This work demonstrates the applicability of this model in the simulation of the riparian vegetation dynamic distribution over a wide range of environments. As it performs in a robust manner and with good results in reaches with different hydrological characteristics, the model could be also applied to analyse different hydrological scenarios or to predict changes after restoration measures within a reach. Copyright © 2012 John Wiley & Sons, Ltd.