Impact of wetland restoration on river discharge - A case study of Bråån, Skåne, Sweden

Abstract: Land use change is a factor not often considered when modeling river discharge in regard to future flood risk. The restoration of wetlands is an ongoing land use change which affects water storage capacity in the soils of a catchment and could lead to lower flows in rivers. This study analysed the effect of an increased wetland area on river discharge in the Bråån catchment in Skåne, Sweden. Discharge was modeled with the HYPE model, developed by the Swedish Meteorological and Hydrological Institute (SMHI). Input data included land use and soil type data, which are classified into soil-land use classes, as well as climate, discharge and elevation data. Wetlands were modeled as constructed internal wetlands with water regulation capability. A GIS-analysis for future potential wetland areas from The County Administrative Board of Skåne (Länsstyrelsen Skåne) served as the base for a realistic wetland increase scenario. River discharge decreased by 2% with the realistic increase. The main reasons for the reduction of discharge are the increase in peat soils and higher evaporation. However, soil and land use parameter values could be improved, and a more complex incorporation of HYPE’s routines could be done to achieve a better model fit. The small reduction in discharge implicates that land use change in form of more wetlands does have an effect on river flow. This should be considered in e.g. future flood mapping and hydrological modeling.