Climate change impacts on river runoff in Latvia

Abstract

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 ) 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 evapotranspiration) 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.

Dryness dynamics of the Baltic Sea region

“…An indirect proof of the decreasing trends of drought recurrence, but not in severity is given by the changes in temperature extremes in the region Fischer, Schär 2009;, as well as changes in the freshwater runoffs and in the river flow across the Baltic Sea (Graham 2004;Kriaučiūnienė et al 2008;Apsīte et al 2011;Hänninen, Vuorinen 2011). The uncertainties of dryness dynamics, however, are still under investigation (Lehner, Döll 2001;Rowell, Jones 2006;Graham et al 2007;Kundzewicz 2009 .…”

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

“…We have obtained comparatively good calibration results for the small and large river basins and calibration periods from 11 to 30 years which allow the use of the hydrological model HBV in further study. In order to compare the results of our studies with other recent studies (Rogozova 2006;Kriaučiūnienė et al 2008;Bethers, Sennikovs 2009;Kurpniece et al 2010;Apsite et al 2011) done in the East Baltic countries we have searched for similar studies dealing with predicted changes in the river runoff regime based on the climate data series taken from the RCM RCAO. In an earlier study done in Latvia by Rogozova (2006), the results from two Latvian river basins, namely, the Irbe and the Gauja, have been compared, and the climate data series are based on the RCM RCAO using two different GCMs and emission scenarios (A2, B2) and the hydrological model HBV.…”

“…Having analysed the calibration results and river runoff simulation of the HBV model in this study and the METQ2007BDOPT model by Apsite et al (2011) regarding the same river basins, generally, we have obtained a slightly better calibration results with the HBV model for the rivers Imula, Bērze, Iecava; the results are the same for the river Salaca; and the result is lower for the river Vienziemīte. Moreover, for both hydrological models one of the drawbacks of the calibrating of the model based upon daily observations is that the resulting hydrographs tend to be somewhat smoothed, as runoff peaks are dampened in the model, while low flows tend to be overestimated.…”

“…Dankers et al (2007Dankers et al ( , 2008 have found stronger increase in the annual river runoff in the Western part of Latvia than in the others. However, on the basis of the latest studies in Latvia by Rogozova (2006), Bethers and Seņņikovs (2009), Apsite et al (2011) and in Lithuania by Kriaučiūnienė et al (2008), the main trend in the climate and river runoff change at the end of the 21 st century is shifted rather towards the southern region forecast of the Baltic Sea basin according to the study by Graham (2004). This leads to the intensification of the hydrological cycle with more precipitation and evapotranspiration under warmer and wetter climate and decrease in the annual river runoff at the end of this century.…”

“…During recent decades, increasing attention has been focused on the studies of the impact of the global climate change on the hydrological cycle in order to evaluate and predict the changes in water resources at various spatial and temporal scales (Rummukainen et al 2003;Andreasson et al 2004;Beldring et al 2008;Yang et al 2010;Thorsteinsson, Björnsson 2011), including in the Baltic region (Jaagus et al 1998;Kriaučiūnienė et al 2008;Kriaučiūnienė et al 2009;Bethers, Seņņikovs 2009;Apsite et al 2011).…”