University of Twente Student Theses


Technical Note: Defining prior probabilities for hydrologic model structures in UK catchments

Clements, M. (2013) Technical Note: Defining prior probabilities for hydrologic model structures in UK catchments.

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Abstract:Choosing a suitable model structure, i.e. a set of equations that represent the dominant hydrologic processes of interest, is the starting point for any modelling study. This model structure choice is often guided by experience with a particular model. More recently the focus has shifted to flexible modelling frameworks, which allow structures to be chosen based on the specific characteristics of the catchment under study. Little work has been done though on defining prior probabilities for different model structures based on physical catchment characteristics or climatic conditions. Here we combine two soil moisture accounting (SMA) modules used widely in the UK, PDM and Penman, in combination with three different routing modules, linear, parallel and leaky, and apply them to 89 UK catchments to define such prior probabilities. The 6 model structure combinations are applied in a Monte Carlo framework (10,000 parameter samples per structure) to each of the catchments and the fraction of parameter sets that are behavioural is estimated. Parameter sets are considered behavioural if they reach pre-­‐defined thresholds regarding Nash-­‐Sutcliffe Efficiency and Bias. We make the basic assumption that better model structures produce more behavioural parameter sets. We find that there is a clear distinction between model structures for different catchment types. A subsequent CART analysis quantifies how physical (baseflow index) and climatic (runoff coefficient) characteristics define which model structures are most likely. We conclude that specific model structures work best for different catchments. We found that there is a certain classification of catchments possible per model structure combination. This classification can be determined by climate, topography, landuse and geology. Geology (BFI) in this case, determines which SMA module to use, while topography (DPSBAR), landuse and climate (Runoff Coefficient) determine which routing module to use.
Item Type:Essay (Bachelor)
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering BSc (56952)
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