The climate change impact on the water balance of the Curonian Lagoon

The Curonian Lagoon is the biggest fresh water basin in Lithuania influenced by the exchange of the fresh Nemunas and other smaller rivers’ water and saline water of the Baltic Sea. The lagoon ecosystem is influenced by fresh, brackish and brackish water masses. A long-term water balance of the Curonian Lagoon was calculated for the period of 1960–2009. The sum river inflow is 21.784 km³/year, precipitation—1.199 km³/year, evaporation—1.007 km³/year, inflow of brackish water from the Baltic Sea to the Curonian Lagoon—6.171 km³/year, and fresh water runoff from the Curonian Lagoon to the Baltic Sea—27.642 km³/year. The lagoon water balance elements have been influenced by climate change. The water balance forecasting has been performed for the period of 2011–2100. The climate change impact on the water balance of the Lagoon has been evaluated using Global Climate Models (ECHAM5 and HadCM3), greenhouse gas emission scenarios (A2, A1B and B1), and hydrological modelling by Hydrologiska Byrans Vattenbalansavdelning (HBV) software. One scenario was selected for the prediction of the Baltic Sea water level. Considerable changes of the Curonian Lagoon water balance are forecasted in the 21st century. Increase of weather temperature and changes in precipitation will influence the elements of water balance of the Curonian Lagoon. In the period of 2011–2100, the river inflow and outflow from the Baltic Sea into the Lagoon will decrease respectively by 20.4 and 16.6% in comparison with the baseline period (1961–1990). The amount of precipitation and evaporation will increase respectively by 3.8 and 25.1%, while inflow from the Baltic Sea into the Curonian Lagoon will increase up to 39.7% in comparison with the baseline period.