 A study by the Azerbaijan Academy of Sciences estimated that the level of the sea was dropping by more than six centimetres per year due to increased evaporation due to rising temperatures caused by climate change.The Volga River, the largest in Europe, drains 20% of the European land area and is the source of 80% of the Caspian's inflow.Its lower reaches are heavily developed with numerous unregulated releases of chemical and biological pollutants.