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Information - HS33 Parameterisation strategies for distributed hydrological modelling across scales
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Event Information |
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In recent years, distributed hydrological models have been widely used in order to take into account the spatial heterogeneity within a catchment. General methodologies related to parameterisation, calibration, verification and validation of distributed models have been subject to considerable discussion and dispute during the last decade. Moreover, although in some applications it is sufficient to model only catchment outflow, growing concerns in pollution and water management require outputs at various points and scales in a catchment, taking into account both surface and groundwater flow as these are the driving mechanisms of solute and sediment transport. These processes are very sensitive to the model parameters such as the hydraulic properties of the soil, the aquifer and the channel network, the geometric properties of hillslopes and the channel network, the vegetation cover, and the initial conditions of soil moisture and watertable. The representativeness of measured parameters and model equations depend on the spatial scale : the local experiment scale (100 cm² - 1 m²), the hillslope and the elementary catchment scale (0.1 - 5 km²) which represents the runoff genesis scale, and the catchment scale ( 5 - 1000 km²) which is the water management scale. It depends also on temporal scale : the runoff genesis (1 minute - 1 day), the annual water cycle (year) and the effects of land use change (few years). In the calibration of distributed models it is important to evaluate the distributed model behaviour rather than just the catchment-integrated behaviour by calibration against catchment outflow. Multi-site and multi-variable calibration should be performed if distributed predictions are needed for different hydrological variables.
The aim of this session is to provide a discussion between field hydrologists and modellers on:
i) the strategies of parameter estimation for distributed models;
ii) the physical representativeness of parameters across spatial and temporal scales;
iii) the scale effects on mathematical representation of hydrological process descriptions;
iv) the effects of basin subdivision into elementary grids or hydrological units, and time discretization, on model performances and parameter values;
v) the problems related to multiscale verification and validation approaches.
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