Water dynamics and evaporation losses to inflows into transboundary Mediterranean lakes – the case of Prespa Lakes

Stable isotope techniques (<i>δ</i>¹⁸Ο, <i>δ</i>²Η of H₂O) were applied in the transboundary Prespa Lakes (Great and Little Prespa) to assess the water dynamics and the evolution of evaporation losses over the past several decades. The lakes currently experience high evaporation losses to inflows (E/I &gt; 60%), which are significantly higher than in the 1980s. The results showed that the Great Prespa Lake (GPL) water level decline could be due to a drastic decrease in lake inflows over evaporation over the years due to climate change and water abstractions. River runoff contributed more (~57%) to the recharge of the GPL in the wet period, whereas in the dry period direct precipitation was more significant. Our work highlights the advantage of using stable isotope techniques to address hydrological problems in comparison to conventional methods, and the need for collaborative efforts between countries to ensure sustainable usage of transboundary water resources.