Hydrological Modelling and River Basin Management - Doctoral Thesis - Jens Christian Refsgaard
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The publications and material presented in this thesis describe a series of scientific investigations on catchment modelling in relation to water resources management. Each of the 15 publications represents parts of the overall topic ranging from development of new concepts and model codes to model applications; from point scale to catchment scale; from flow modelling to transport and reactive modelling; from planning type applications to real-time forecasting and further on to crosscutting issues and protocols for the modelling process.
The thesis starts with a presentation of protocols for the hydrological modelling process together with a discussion of the interaction between the water resources planning and management process and the hydrological modelling process. This includes a definition of terminology, a discussion of the underlying scientific philosophy and a classification of hydrological models. The following chapter comprises summaries of cases of simulation models based on nine of the publications. The post evaluations of the contributions to scientific knowledge in the publications and the issues not taken into account in the earlier publications reveal significant developments over the years. For example the first publications focussing on development of new model codes did not put any emphasis on rigorous verification or validation tests nor on uncertainty assessments, which are key issues today. The cases furthermore illustrate how general issues such as scaling and model validation gradually emerged from experiences and problems encountered in catchment studies that had other primary objectives. The next chapter then provides a presentation and discussion of four general issues: (a) catchment heterogeneity and scaling; (b) confirmation, verification, calibration and model validation; (c) uncertainty assessment; and (d) quality assurance in model based water management.
My main contributions to scientific knowledge have been in the following five areas:
- New conceptual understanding and code development. The Suså model was based on a new conceptual understanding of the surface water/groundwater interaction in moraine catchment and brought new insight into the effect of groundwater abstraction on streamflow in catchments with such hydrogeological characteristics.
- Model validation. The work on rather rigorous principles for model validation and the examples of their application both for lumped conceptual and distributed physically based models is a cornerstone in my research. In particular the introduction of the term 'conditional validation' is novel.
- Scaling. The framework on scaling does not 'solve' the scaling problem but contributes to clarifications on applicable methodologies with focus on their respective assumptions and limitations.
- Uncertainty assessment. During the past decade a considerable part of my research work has focussed on uncertainty aspects. I consider my main contributions in this respect to be the introduction of the broader uncertainty aspects integrated into the modelling framework and the work with model structure uncertainty.
- Modelling protocols and guidelines for quality assurance in the modelling process. The comprehensive modelling protocol developed within the HarmoniQuA project is a formalisation of experience and practises that have gradually emerged over the years. The novel elements are the emphasis on (a) the interactive dialogue between modeller, water manager, reviewer, stakeholders and the public; (b) uncertainty assessments throughout the modelling process; (c) model validation; and (d) experience and subjective knowledge introduced through external model reviews.