Climate change impacts on river runoff in Latvia

In order to assess climate change impacts on river runoff patterns at the end of this century, the hydrological model METQ2007BDOPT was applied to 8 river basins and sub-basins in Latvia, which is a part of the southeast Baltic Sea basin. The climate data we used originate from the PRUDENCE project and were prepared in a separate study. Changes in hydro-climate were analysed using one control run (1961-1990) and 2 IPCC scenario runs (A2 and B2; 2071-2100). For the A2 scenario, both annual and seasonal analysis predicted the major significant changes in most cases. For both scenarios, an increase of the mean annual climate data (air temperature, precipitation and evapo transpiration) is forecast, whereas the mean annual river runoff is predicted to decrease. The seasonal runoff pattern is expected to change towards significantly higher runoff during winter, following a decrease in spring and autumn. Maximum river discharge will occur in winter instead of spring. No considerable change in streamflow is predicted for summer. Future climate will change, leading to modifications in the river runoff regime and the shape of the hydrograph, which will be similar to that of the present Western European rivers, i.e. 2 principal periods instead of 4: one with high flow, mostly falling in the cold period of the year; and one with low flow, mostly in the warm period.