Hydrological downscaling

Hydrological results calculated simultaneously all over Europe necessarily contain compromises in model results locally. Hydrological downscaling allows the user to develop an improved, local version of the hydrological model from the pan-European model.

This is done by extracting a local version of the model which includes all subbasins upstream of the point-of-interest (for example at a stretch of river within the city that is sensitive to flooding). This local version of the model is then automatically recalibrated to the nearest gauging data (measured river discharge data).

The user may add their own measured river discharge data within the local model domain for improved calibration. The recalibrated local model can then be used simulate local hydrological scenarios using the climate scenarios as inputs.

E-HYPE: Pan-European simulation of river discharge

Hydrological results, both pan-European and local are calculated using the HYPE hydrological model. HYPE, (Hydrological Predictions for the Environment) is a semi-distributed processed-based hydrological model for small-scale and large-scale assessments of water resources and water quality.

The SUDPLAN model version simulates surface runoff, macropore flow, tile drainage, groundwater outflow from the individual soil layers and accumulated river runoff. The model code is structured so that the model can easily be applied with high resolution over large model domains, which is facilitated by linking coefficients to physical characteristics and using a homogenous calibration procedure across the entire model domain.

The pan-European hydrological database in Common Services is generated by running the water part of the HYPE model in a multi-basin European application (E-HYPE). The E-HYPE model domain covers most of the European continent, from the British Isles to the Ural Mountains, and from Norway to the Mediterranean Sea, divided into subbasins with a median resolution of around 250 km2. The extracted local model has the same subbasins as the pan-European model and the starting point for the automatic recalibration of the local model uses the calibration parameter set valid at pan-European scale.

Upload of local water discharge contributes to improved model output

In order to facilitate the local hydrological downscaling using the Common Services Tool, the local user will select their point-of-interest from the pan-European model. This should be a point on a river or stream for which the upstream catchment will be locally modelled.

Furthermore, the user may include one or more monitored time-series of water discharge within the catchment. In this case, the user must click on the subbasin nearest to the gauge location. It will then be possible to run a simple automatic calibration routine for this domain to improve the multi-basin scale calibration. This will improve the model performance for the specific river of interest.

The user can then select input data (precipitation and temperature) from the climate scenarios which have been bias-corrected and downscaled (see above).