Ignacio Andrés-Doménech

Analysis of monitoring programmes and their suitability for ecotoxicological risk assessment in four Spanish basins.

Data from four Spanish basin management authorities were analysed. Chemical and biological data from four Spanish basin management authorities were analysed, focusing on three consecutive years. Aims were to i) determine the chemicals most likely responsible for the environmental toxicological risk in the four Spanish basins and ii) investigate the relationships between toxicological risk and biological status in these catchments. The toxicological risk of chemicals was evaluated using the toxic unit (TU) concept. With these data we considered if the potential risk properly reflects the risk to the community or, alternatively, if new criteria should be developed to improve risk assessment. Data study revealed inadequacies in processing and monitoring that should be improved (e.g., site coincidence for chemical and biological sampling). Analysis of the chemical data revealed high potential toxicological risk in the majority of sampling points, to which metals were the main contributors to this risk. However, clear relationships between biological quality and chemical risk were found only in one river. Further investigation of metal toxicity may be necessary, and future analyses are necessary to accurately estimate the risk to the environment.

Efficiency of Storm Detention Tanks for Urban Drainage Systems under Climate Variability

Climate change effects on combined sewer systems efficiency is a great matter of concern. In fact, changes in rainfall regime could significantly affect combined sewer overflows (CSOs) into receiving water bodies. Given that CSOs are a significant source of pollution, a better understanding and modeling of climate change effects on urban drainage systems is a compelling requirement to support design of adaptation strategies. This paper aims at studying the resilience of storm water detention tanks efficiency with respect to changes in rainfall forcing. In detail, an analytical probabilistic model is proposed to assess overflow reduction efficiency and volumetric efficiency of detention tanks depending on behaviors of climate and urban catchment. Sensitivity of tank efficiencies is evaluated under assigned changes in rainfall forcing. Results show that resilience of storm tanks benefits from filtering of climate change effects operated by the urban catchment.

Prediction of Evapotranspiration in a Mediterranean Region Using Basic Meteorological Variables

AbstractA critical need for farmers, particularly those in arid and semiarid areas is to have a reliable, accurate and reasonably accessible means of estimating the evapotranspiration rates of their crops to optimize their irrigation requirements. Evapotranspiration is a crucial process because of its influence on the precipitation that is returned to the atmosphere. The calculation of this variable often starts from the estimation of reference evapotranspiration, for which a variety of methods have been developed. However, these methods are very complex either theoretically and/or because of the large amount of parameters on which they are based, which makes the development of a simple and reliable methodology for the prediction of this variable important. This research combined three concepts such as cluster analysis, multiple linear regression (MLR), and Voronoi diagrams to achieve that end. Cluster analysis divided the study area into groups based on its weather characteristics, whose locations were t...

Characterization of wash-off from urban impervious surfaces and SuDS design criteria for source control under semi-arid conditions

Knowledge about pollutant wash-off from urban impervious surfaces is a key feature for developing effective management strategies. Accordingly, further information is required about urban areas under semi-arid climate conditions at the sub-catchment scale. This is important for designing source control systems for pollution. In this study, a characterization of pollutant wash-off has been performed over sixteen months, at the sub-catchment scale for urban roads as impervious surfaces. The study was conducted in Valencia, Spain, a city with a Mediterranean climate. The results show high event mean concentrations for suspended solids (98mg/l), organic matter (142mgCOD/l, 25mgBOD5/l), nutrients (3.7mgTN/l, 0.4mgTP/l), and metals (0.23, 0.32, 0.62 and 0.17mg/l for Cu, Ni, Pb, and Zn, respectively). The results of the runoff characterization highlight the need to control this pollution at its source, separately from wastewater because of their different characteristics. The wash-off, defined in terms of mobilized mass (g/m2) fits well with both process-based and statistical models, with the runoff volume and rainfall depth being the main explanatory variables. Based on these results and using information collected from hydrographs and pollutographs, an approach for sizing sustainable urban drainage systems (SuDS), focusing on water quality and quantity variables, has been proposed. By setting a concentration-based target (TSS discharged to receiving waters <35mg/l), the results indicate that for a SuDS type detention basin (DB), an off-line configuration performs better than an on-line configuration. The resulting design criterion, expressed as SuDS volume per unit catchment area, assuming a DB type SuDS, varies between 7 and 10l/m2.

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.

A High-Order Well-Balanced Central Scheme for the Shallow Water Equations in Channels with Irregular Geometry

This paper presents a new numerical scheme based on the finite volume method to solve the shallow water equations in channels with rectangular section and variable width. Time integration is carried out by means of a Runge-Kutta scheme with a natural continuous extension, using a new temporary forward flow at the midpoint of each cell which considers the physical flow and the source term primitive of the shallow water model. That term takes into account the gradient of bed height, channel width and friction energy loss model. Spatial integration is based on a central scheme in which flows only have to be evaluated on the midpoint of the cells where the solution is reconstructed. In this way, it is not necessary to know the structure of the partial differential equations to be solved. A centered three degree reconstruction polynomial is applied, using a slope correction to the midpoint of each cell to prevent the occurrence of spurious numerical oscillations. Some benchmark examples show the non-oscillatory behavior of numerical solutions in channels with a variable width. A comparison between numerical results and those obtained experimentally on a laboratory flume is also carried out.

Two-Dimensional Hydraulic Modeling and Analysis of Morphological Changes in the Palancia River (Spain) During a Severe Flood Event on October 2000

This paper analyzes the possibilities that mathematical models offer to reconstruct flood events, and to predict their erosional and sedimentary effects. To that end, the severe flood event of October 2000 of the Palancia River (Valencia, Spain) is assessed. The hydraulic reconstruction was performed with the software GUAD 2D, a two-dimensional mathematical simulation model for shallow water conditions. The results obtained from the mathematical model and the hydraulic-sedimentological analysis were compared with the flood-related features mapped by means of geomorphologic photo-interpretation and field observations. This comparative study illustrates that these models constitute a powerful tool for the prediction of the river bed evolution. Calibration was the most challenging stage in the reconstruction of this historical event.

Nitrogen in Infiltrated Water from Pervious Pavements Under Different Rainfall Regimes and Pollution Build-up Levels

Sustainable urban drainage systems (SUDS) are a nature based solution for best management of rainwater in urban areas. Pervious pavements are one of the SUDS typologies. This study evaluates the water quality filtered by a type of pervious pavement and the influence of the rainfall regime (Atlantic and Mediterranean) and the pollution build-up degree. Total nitrogen (TN) infiltrate concentrations have increased over the study due to the increasing of sediment build-up levels on the pavement surface, with maximum concentrations between 2.7 and 5.0 mg N/l depending on the rainfall regime and the pavement configuration; temperature also influences significantly the leachability of nitrogen. In fact, linear regression models for TN as dependent variable and accumulated mass and temperature have been obtained with a high goodness-of-fit. TN leached over the study represents between 22% and 31% of the total nitrogen present in the sediments accumulated on the pavement surface so the total load is much lower than what would have occurred in an impervious pavement under the same build-up conditions.

Flood risk assessment in urban catchments using multiple regression analysis

AbstractFlood assessment in urban catchments is usually addressed through the combination of geographic information systems (GISs) and stormwater models. However, the coupled use of these tools inv...

Multiple Regression Analysis as a Comprehensive Tool to Model Flood Hazard in Sewersheds

Flood modelling in urban areas is usually undertaken using stormwater tools, which are complex and time-consuming in terms of parametrization. To replace them, this research developed a methodology for predicting flooding probability in urban watersheds (sewersheds) through the modelling of peak flow rates from a set of watershed and sewer network-related factors relevant for the occurrence of floods. This was addressed through the stepped integration of Multiple Linear Regression (MLR), Multiple Nonlinear Regression (MNR) and Multiple Binary Logistic Regression (MBLR). A case study of a sewershed in Espoo (Finland) was used to validate the proposed approach and test it for future estimates, enabling the prediction of flooding probabilities under different Climate Change scenarios.