DEVELOPMENT OF A NEW HYDROLOGICAL MODEL

The HBV model has been the corner-stone for much of the hydrological activities at the SMHI for the past 30 years. A new Windows user-interface has recently been developed for the model (IHMS version 5). The HBV model is very appropriate for forecasting purposes, as a good balance between simplicity and performance. However, the model was originally not intended as a scenario model, with proper process descriptions, water and nutrient flow paths. The simplified evapotranspiration routine in the model makes it difficult to estimate the effects that a change in climate would have on water resources. The model is insensitive to changes in land-use and does not make optimal use of geographical information on topography, land-use, soil types etc. that is available today.

The development of a new, more distributed, model has therefore just begun. The model will be based on the experiences from developments and application of the HBV/PULSE models, but is intended to include:

• Explicit representation of flowpaths for water and nutrients in the model structure
• Layered soil routine with water holding capacities according to soil type
• Soil response units according to combination of soil type and land-use " Evapotranspiration according to vegetation type
• Turn-over of nitrogen and phosphorous in the soil
• A simple and a more detailed atmospheric scheme for coupled simulation of snowmelt and potential evapotranspiration.

Figure 1. Tentative structure of the new model.

Duration: 2005-2007

Funded by: SMHI

Responsible at SMHI: Göran Lindström

External partners: Uppsala University