Drought risk and vulnerability in water supply systems.

This paper provides an overview of the challenges presented to the managers of water supply systems by drought and water scarcity. Risk assessment is an essential tool for the diagnostic of water scarcity in this type of systems. The evaluation of the risk of water shortage is performed with the use of complex mathematical models. Different alternatives to address the problem are presented, covering a range of methodological approaches. The actions adopted to prevent or mitigate the effects of water scarcity should be properly organized in drought management plan. The process of development and implementation of drought management plans is briefly described presenting several examples taken from the Mediterranean region

Análisis de los posibles hidrogramas producidos por la rotura de la presa de puentes

En la ponencia se presenta un análisis de los posibles hidrogramas originados por la rotura de la presa de Puentes. Se ha elaborado un modelo simplificado de vaciado del embalse, al que se han aplicado distintas condiciones de contorno. Se ha estudiado el posible sifonamiento de la cimentación y su posterior tubificación, obteniendo las leyes de caudales en función del tiempo a medida que progresa el proceso. Una vez formado el orificio, se ha analizado la ley de vaciado del embalse. Como resultado se han obtenido conclusiones respecto al proceso de rotura de la presa, a partir de la descripción de su vaciad

Design flood hydrographs from the relationship between flood peak and volume

Hydrological frequency analyses are usually focused on flood peaks. Flood volumes and durations have not been studied as extensively, although there are many practical situations, such as when designing a dam, in which the full hydrograph is of interest. A flood hydrograph may be described by a multivariate function of the peak, volume and duration. Most standard bivariate and trivariate functions do not produce univariate three-parameter functions as marginal distributions, however, three-parameter functions are required to fit highly skewed data, such as flood peak and flood volume series. In this paper, the relationship between flood peak and hydrograph volume is analysed to overcome this problem. A Monte Carlo experiment was conducted to generate an ensemble of hydrographs that maintain the statistical properties of marginal distributions of the peaks, volumes and durations. This ensemble can be applied to determine the Design Flood Hydrograph (DFH) for a reservoir, which is not a unique hydrograph, but rather a curve in the peak-volume space. All hydrographs on that curve have the same return period, which can be understood as the inverse of the probability to exceed a certain water level in the reservoir in any given year. The procedure can also be applied to design the length of the spillway crest in terms of the risk of exceeding a given water level in the reservoi

A bivariate return period based on copulas for hydrologic dam design: accounting for reservoir routing in risk estimation

A multivariate analysis on flood variables is needed to design some hydraulic structures like dams, as the complexity of the routing process in a reservoir requires a representation of the full hydrograph. In this work, a bivariate copula model was used to obtain the bivariate joint distribution of flood peak and volume, in order to know the probability of occurrence of a given inflow hydrograph. However, the risk of dam overtopping is given by the maximum water elevation reached during the routing process, which depends on the hydrograph variables, the reservoir volume and the spillway crest length. Consequently, an additional bivariate return period, the so-called routed return period, was defined in terms of risk of dam overtopping based on this maximum water elevation obtained after routing the inflow hydrographs. The theoretical return periods, which give the probability of occurrence of a hydrograph prior to accounting for the reservoir routing, were compared with the routed return period, as in both cases hydrographs with the same probability will draw a curve in the peak-volume space. The procedure was applied to the case study of the Santillana reservoir in Spain. Different reservoir volumes and spillway lengths were considered to investigate the influence of the dam and reservoir characteristics on the results. The methodology improves the estimation of the Design Flood Hydrograph and can be applied to assess the risk of dam overtoppin

Improving probabilistic flood forecasting through a data assimilation scheme based on genetic programming

Opportunities offered by high performance computing provide a significant degree of promise in the enhancement of the performance of real-time flood forecasting systems. In this paper, a real-time framework for probabilistic flood forecasting through data assimilation is presented. The distributed rainfall-runoff real-time interactive basin simulator (RIBS) model is selected to simulate the hydrological process in the basin. Although the RIBS model is deterministic, it is run in a probabilistic way through the results of calibration developed in a previous work performed by the authors that identifies the probability distribution functions that best characterise the most relevant model parameters. Adaptive techniques improve the result of flood forecasts because the model can be adapted to observations in real time as new information is available. The new adaptive forecast model based on genetic programming as a data assimilation technique is compared with the previously developed flood forecast model based on the calibration results. Both models are probabilistic as they generate an ensemble of hydrographs, taking the different uncertainties inherent in any forecast process into account. The Manzanares River basin was selected as a case study, with the process being computationally intensive as it requires simulation of many replicas of the ensemble in real time

Effect of radar rainfall time resolution on the predictive capability of a distributed hydrologic model

The performance of distributed hydrological models depends on the resolution, both spatial and temporal, of the rainfall surface data introduced. The estimation of quantitative precipitation from meteorological radar or satellite can improve hydrological model results, thanks to an indirect estimation at higher spatial and temporal resolution. In this work, composed radar data from a network of three C-band radars, with 6-minutal temporal and 2 × 2 km2 spatial resolution, provided by the Catalan Meteorological Service, is used to feed the RIBS distributed hydrological model. A Window Probability Matching Method (gage-adjustment method) is applied to four cases of heavy rainfall to improve the observed rainfall sub-estimation in both convective and stratiform Z/R relations used over Catalonia. Once the rainfall field has been adequately obtained, an advection correction, based on cross-correlation between two consecutive images, was introduced to get several time resolutions from 1 min to 30 min. Each different resolution is treated as an independent event, resulting in a probable range of input rainfall data. This ensemble of rainfall data is used, together with other sources of uncertainty, such as the initial basin state or the accuracy of discharge measurements, to calibrate the RIBS model using probabilistic methodology. A sensitivity analysis of time resolutions was implemented by comparing the various results with real values from stream-flow measurement stations

Respuestas de adecuación ante los escenarios de cambio climático

La perspectiva del cambio climático abre numerosos interrogantes sobre las políticas de adaptación que resultarán más apropiadas a medio y largo plazo en el sector de la gestión de recursos hídricos. A pesar de que existe un amplio consenso en el mundo científico sobre la posible evolución de las temperaturas y precipitaciones a escala regional, resulta todavía muy difícil cuantificar el impacto que éstas tendrán sobre la disponibilidad de recursos hídricos a escala local. Los últimos estudios realizados en España concluyen que el cambio climático supondrá una presión adicional a las muchas que ya se ejercen sobre los sistemas de explotación de recursos hídricos. En esta ponencia se pasa revista a un abanico de medidas de adaptación que se consideran apropiadas para reaccionar a la nueva situación creada por el cambio climático. Estas políticas pueden verse como una colección de buenas prácticas o principios generales, cuya aplicación en el tiempo dependerá en gran medida de la iniciativa de los poderes públicos, de la evolución de la situación climática y de su percepción por parte de los usuarios

Previsiones para España según los últimos estudios de cambio climático

En este capítulo se describen las perspectivas de evolución de los recursos hídricos en España según los últimos estudios realizados sobre cambio climático. Se analizan los resultados del proyecto PRUDENCE, que es un proyecto europeo reciente, dedicado a la elaboración de proyecciones regionalizadas de cambio climático en Europa para finales del siglo XXI, basadas en los escenarios de emisiones A2 y B2 del Informe Especial de Escenarios de Emisiones del Panel Intergubernamental para el Cambio Climático (IPCC). Se ha procedido al análisis de datos de escorrentía media mensual resultantes del citado proyecto relativos a la España peninsular, comparándolos con los datos de aportaciones medias mensuales del estudio de recursos recogido en el Libro Blanco del Agua en España, con la doble finalidad de evaluar la capacidad de los modelos para reproducir la hidrología española y de analizar sus proyecciones sobre el impacto global del cambio climático en los recursos hídricos de España. Los resultados obtenidos indican que, a pesar del alto grado de incertidumbre que tienen las proyecciones climáticas, la mayor parte de los modelos regionales de clima utilizados en el proyecto Prudence coinciden en señalar disminuciones muy significativas de las aportaciones en régimen natural, lo que tendrá indudables impactos sobre la futura gestión de nuestros recursos hídrico

Comparison of methods for downscaling runoff from regional climate models in Spanish basins

At present there is much literature that refers to the advantages and disadvantages of different methods of statistical and dynamical downscaling of climate variables projected by climate models. Less attention has been paid to other indirect variables, like runoff, which play a significant role in evaluating the impact of climate change on hydrological systems. Runoff presents a much greater bias in climate models than other climate variables, like temperature or precipitation. It is very important to identify the methods that minimize bias while downscaling runoff from the gridded results of climate models to the basin scal

Modelo de simulación de la operación de un embalse en avenida y su integración al sistema FEWS

En este trabajo se presentan dos modelos de gestión de embalses en avenidas, el primero, basado en reglas de operación de los órganos de desagüe definidas por el usuario y, el segundo, correspondiente al método de gestión programada de embalses de Girón. Se incluye además un módulo que integra ambos métodos al sistema hidrometeorológico de alerta temprana FEWS