Andreas Schumann

Panta Rhei-Everything Flows: Change in hydrology and society-The IAHS Scientific Decade 2013-2022

Abstract The new Scientific Decade 2013–2022 of IAHS, entitled “Panta Rhei—Everything Flows”, is dedicated to research activities on change in hydrology and society. The purpose of Panta Rhei is to reach an improved interpretation of the processes governing the water cycle by focusing on their changing dynamics in connection with rapidly changing human systems. The practical aim is to improve our capability to make predictions of water resources dynamics to support sustainable societal development in a changing environment. The concept implies a focus on hydrological systems as a changing interface between environment and society, whose dynamics are essential to determine water security, human safety and development, and to set priorities for environmental management. The Scientific Decade 2013–2022 will devise innovative theoretical blueprints for the representation of processes including change and will focus on advanced monitoring and data analysis techniques. Interdisciplinarity will be sought by increased efforts to connect with the socio-economic sciences and geosciences in general. This paper presents a summary of the Science Plan of Panta Rhei, its targets, research questions and expected outcomes. Editor Z.W. Kundzewicz Citation Montanari, A., Young, G., Savenije, H.H.G., Hughes, D., Wagener, T., Ren, L.L., Koutsoyiannis, D., Cudennec, C., Toth, E., Grimaldi, S., Blöschl, G., Sivapalan, M., Beven, K., Gupta, H., Hipsey, M., Schaefli, B., Arheimer, B., Boegh, E., Schymanski, S.J., Di Baldassarre, G., Yu, B., Hubert, P., Huang, Y., Schumann, A., Post, D., Srinivasan, V., Harman, C., Thompson, S., Rogger, M., Viglione, A., McMillan, H., Characklis, G., Pang, Z., and Belyaev, V., 2013. “Panta Rhei—Everything Flows”: Change in hydrology and society—The IAHS Scientific Decade 2013–2022. Hydrological Sciences Journal. 58 (6) 1256–1275.

Probability Analysis of Hydrological Loads for the Design of Flood Control Systems Using Copulas

The natural variability of floods cannot be represented appropriately by single design floods. Different hydrological scenarios are needed for sustainable design of flood protection structures such as flood control reservoirs and polders. In this paper a method to estimate the probability of generated hydrological scenarios for the risk analysis of a flood control system is presented. Bivariate probability analyses of different flood variables using copulas are applied to overcome the problem that univariate probability analysis may lead to an over- or underestimation of the hydrological risk. The mesoscale Unstrut river basin in Germany, which consists of two reservoirs located downstream of the main tributaries and flood polders, serves as test case. The spatial distribution of flood events within the river basin is analyzed by the joint probability of the inflow peaks at the two reservoirs. Furthermore, in a second application copulas are used for risk analysis of the individual flood detention structu...

Application of a geographic information system for conceptual rainfall-runoff modeling.

Abstract Geographic information systems (GIS) offer many new opportunities for hydrological modeling. They can be used to form spatially distributed models of watershed. However, some problems of this approach, e.g. the parameterization of physically based models, are not resolved yet. Conceptual models of the meso-scale still have a great practical importance. In this paper one approach is presented: how statistical descriptions of distributed catchment characteristics could be used to consider spatial heterogeneity within conceptual models. Three semi-distributed modules are presented. The three components are combined to a hydrological model including feedback components between surface flow and infiltration and between subsurface return flow and surface flow in saturated areas. The model was set up to use spatially distributed information about catchment characteristics for the estimation of its parameters. By a direct estimation of some model parameters from a GIS-based analysis of the catchment characteristics, the number of calibration parameters can be reduced. In the second part it is shown how the application of this model to different catchments within a region can benefit from boundary conditions for optimization, which are derived from a GIS considering the differences of catchment characteristics.

Development of conceptual semi-distributed hydrological models and estimation of their parameters with the aid of GIS

Abstract Conceptual semi-distributed hydrological models are developed for a limited consideration of spatial heterogeneity of hydrological characteristics within a river basin. This heterogeneity can be described by area distribution functions of hydrological characteristics which can be estimated in a most effective way by a Geographical Information System (GIS). It is shown how the application of a GIS can support the development and the calibration of a conceptual hydrological model. GIS information is used to establish the criteria for sub-division of the river basin and for estimation of model structures (especially for further horizontal divisions of each basin into more homogeneous parts). That information is also used for estimation of basin characteristics and their differences between sub-basins as a support for parameter calibration by optimization. The methodology presented can be used for the development of a model structure on an objective basis and for model calibration which considers the...

Markov cross-correlation pulse model for daily streamflow generation at multiple sites

On the basis of the Markov cross-correlation pulses (MCCP) assumption, a stochastic model for daily streamflow generation at multiple sites by integrating random occurrences of wet and dry spells is formulated in this paper. These pulses are supposed to concurrently occur with Markovian correlation at different gauges. Daily streamflow, assumed being transferred from this kind of unobserved pulses occurred over the river basin, is represented by the convolution of a response function with variable parameters and the lag-1 Markov correlation pulses with random cross-correlative residuals. The fitting of the model and the simultaneous generation of synthetic daily streamflow at multiple sites are verified with a case study at Wupper River in Germany. Daily streamflow sequences generated from the model are compared against historical records, and the result from hypothesis test shows that the MCCP model could provide satisfactory synthetic streamflow sequences for the multiple sites of interest.

Robust flood statistics: comparison of peak over threshold approaches based on monthly maxima and TL-moments

ABSTRACT Flood quantile estimation based on partial duration series (peak over threshold, POT) represents a noteworthy alternative to the classical annual maximum approach since it enlarges the available information spectrum. Here the POT approach is discussed with reference to its benefits in increasing the robustness of flood quantile estimations. The classical POT approach is based on a Poisson distribution for the annual number of exceedences, although this can be questionable in some cases. Therefore, the Poisson distribution is compared with two other distributions (binomial and Gumbel-Schelling). The results show that only rarely is there a difference from the Poisson distribution. In the second part we investigate the robustness of flood quantiles derived from different approaches in the sense of their temporal stability against the occurrence of extreme events. Besides the classical approach using annual maxima series (AMS) with the generalized extreme value distribution and different parameter estimation methods, two different applications of POT are tested. Both are based on monthly maxima above a threshold, but one also uses trimmed L-moments (TL-moments). It is shown how quantile estimations based on this “robust” POT approach (rPOT) become more robust than AMS-based methods, even in the case of occasional extraordinary extreme events. Editor M.C. Acreman Associate editor A. Viglione

Copulas – New Risk Assessment Methodology for Dam Safety

Consideration of a broad range of hydrological loads is essential for risk-based flood protection planning. Furthermore, in the planning process of technical retention facilities it is necessary to use flood events, which are specified by several characteristics (peak, volume and shape). Multivariate statistical methods are required for their probabilistic evaluation. Coupled stochastic-deterministic simulation may be applied to generate a runoff time series, since the required amount of data is generally not available. Even the effect of complex flood protection systems may be evaluated through generation of a data base by means of stochastic-deterministic simulations with subsequent statistical analysis of the individual hydrological load scenarios. Multivariate frequency analyses of correlated random variables are useful to specify these scenarios statistically. Copulas are a very flexible method to estimate multivariate distributions, because the marginal distributions of the random variables can differ. Here a methodology for flood risk assessment is presented which was applied in two case studies in Germany.

Chapter 11 – Workflow oriented participatory decision support for integrated river basin planning

The integrated water-resource management (IWRM) approach considers water as an integral part of ecosystems, a natural resource, and a social and economic good. The European Water Framework Directive (WFD) specifies guidelines for integrated river-basin management that are implementing this holistic view by means of a coherent water policy within all member states of the European Union. Multicriteria methods allow water-resource managers to search for efficient measures, which take into account ecological and socioeconomic criteria according to the preferences of decision makers including stakeholders. Learning-based interactive methods provide a suitable solution for collaborative participatory decision making in a dynamic decision environment such as the implementation of a new directive. The planning cycle of implementation is based on the general scheme of driving forces, pressure, state, impact, and responses (DPSIR) adopted by EEA. A relatively large numbers of criteria have to be considered for assessing the complex interactions between water and society. Decision support systems (DSS) are appropriate tools for this purpose. Considering the variety of stakeholders (with regard to water, everybody is a stakeholder), balancing the interests of various groups could be very difficult. Thats why DSS that are designed to support the implementation of the WFD should be open and interactive usable systems, capable to provide a platform for public discussions of measures among stakeholders.

Chain-dependent Markov correlation pulse model for daily streamflow generation

A stochastic model for the temporal and spatial description of daily streamflow at multiple sites is presented. It is an extension of a chain-dependent process commonly fitted to daily precipitation series. The extension involves allowing daily pulses to be auto- and cross-correlated at temporal and spatial scales. The chain-dependent Markov correlation pulse (CDMCP) model, consisting of a two-state, first-order Markov chain for occurrences and a Markov correlation model for nonzero pulse height, is extended to simultaneous pulse generation at multiple sites. The pulse model coupled with a variable response function was applied to the daily streamflow generation for Wuper River in Germany, and was satisfactory in preserving the short-term structure of the occurrence process, as well as part of the statistics of the seasonal streamflow. The use of Markov model yields good agreement of autocorrelation in the synthetic pulse and streamflow series.

Rainfall Generators for Application in Flood Studies

This chapter discusses various approaches for stochastic rainfall synthesis focusing on methods for generation of short time step precipitation as required for flood studies. A brief introduction motivates the utilisation of rainfall generators for flood modelling. Then special characteristics of rainfall as stochastic process are discussed. The rainfall models presented in the following are classified in alternating renewal models, time series models, point process models, disaggregation and resampling approaches. They are usually applied for continuous unconditional simulation of rainfall series in time and/or in space. Two case studies at the end of the chapter illustrate the application of daily and hourly space-time precipitation models for flood studies.