Forecasted changes in the climate and the river runoff regime in Latvian river basins

The hydrological model HBV (Hydrologiska Byråns Vattenbalansavdelning model) has been applied to six river basins in Latvia to assess climate change and its impacts on the river runoff regime at the end of the 21^st century. Climate change has been predicted by applying the regional climate model RCAO with the driving boundary conditions from the global general circulation model HadAM3H applied for the IPCC scenarios A2 and B2 and the following time periods: 1961-1990 (control) and 2071-2100 (scenario). Changes have been found under both scenarios. Major changes in the future hydro-climate data were forecasted according to the A2 scenario, where the trends of increase are identified for the annual mean air temperature (by 4°C), the precipitation (by 12%) and the evapotranspiration (by 21%), while the river runoff will decrease by 15% at the same time. The changes in the length of the growing season and heavy rainfall have been predicted. Both scenarios forecast changes in the seasonal runoff regime where the major part of the runoff will be generated in winter, followed by spring, autumn and summer. The maximum river discharge will occur in winter instead of spring.