Modelling catchment discharge in Finland in 1951–2099 using transient
Veijalainen, N., Vehviläinen, B., Koivusalo, H. & Korhonen, J.
Climate change impacts on discharge were estimated using hydrological
modelling and transient climate scenarios for 1951-2099. The future
changes in annual and seasonal discharge and annual mean floods were
projected for four catchments in different parts of Finland and with
different hydrological characteristics. The assessment was carried out
using daily air temperature and precipitation series simulated by four
Regional Climate Models (RCMs) as input to a conceptual hydrological
model Watershed Simulation and Forecasting System (WSFS). The daily
data from RCMs was bias corrected with the quantile-quantile mapping
method to remove systematic biases in the meteorological series.
Without bias correction the simulated discharge differed significantly
from the observed discharge, but the bias correction improved the
results considerably. The results showed that seasonal changes,
especially increase in winter runoff, were the most consistent
hydrological impacts of climate change with all the climate scenarios.
Changes in annual mean discharge and high and low flows were only
significant for some individual scenarios. The use of bias corrected
RCM data as input to the hydrological model enables transient
simulations and uses more information from the RCMs compared to the
traditional methods, which use changes of monthly mean values of
temperature and precipitation as the climate change signal for the
hydrological model. However, the simulation results aggregate
considerable uncertainties from the climate modelling, bias correction
and the hydrological model. Further development and evaluation the bias
correction methods are part of an ongoing project at the Finnish
Environment Institute and the Finnish Meteorological Institute.