The large-scale hydrological models developed at SMHI use the spatial distributions of topography, soils, vegetation and nutrient inputs to predict spatially-varying catchment behaviour.
Homogenous model for transboundary waters
Uniform input data from readily available global databases and a uniform approach to model application development and calibration are used over the entire modelled region. This ensures a homogenous model application, for which transboundary rivers and indeed all rivers and streams are treated equally. A high spatial resolution ensures a sufficiently high-resolution description of topography, land-uses, nutrient inputs and soil-types as well as the hydrometeorological forcing, which can vary significantly, particularly in mountainous regions and where convective rainfall events are significant.
Examples of large-scale, high-resolution models we have developed at SMHI include:
Baltic Sea catchment area: BALT-HYPE
La Plata Basin in South America:
Niger river: ,
Arctic Ocean catchment area:
Middle East and northern Africa: MENA-HYPE
A summary of these models can be found at . The hydrological model has been used for all systems described above.
Purpose of models
Results from such models can be used for many different purposes. Discharge and nutrient load results along the coastal boundary of the model domain may be used to examine freshwater and nutrient influxes to seas.
Discharge and water quality results at all points with the model domain can be used for characterization of water body status, establishment of environmental goals, planning of remedial measures and development of monitoring strategies for the European Water Framework Directive (WFD).
The models can also be used to describe variability in hydrological and nutrient load variables in a present climate, but can also be run using climate model data to predict future conditions.
Tool for set-up new models
Research challenges specific to large-scale applications of hydrological and nutrient models include:
• Evaluating and correcting gridded precipitation and temperature data for large regions
• Evaluating and improving topographical databases and river routing networks (e.g. HYDRO1K, HYDROSHEDS) for use at varying scales over large regions
• New methods for uniform calibration of distributed models over large regions
• New methods for evaluation/validation of models across many gauging stations and many land-use, soil-types and climatic regions
• Methods for using climate model precipitation and temperature for large-scale hydrological modelling