Seasonal Temperature Variations of Lake Vrana on the Island of Cres and Possible Influence of Global Climate Changes

Lake Vrana on the island of Cres is one of the largest fresh water features on Mediterranean islands. The maximum depth of the lake is 72 m and it stores 220 million m3 of fresh water. The paper provides an overview of lake and groundwater temperature measurements to date and recent activities within the EU project ＂CC-WaterS （Climate Change and Impacts on Water Supply）＂. Groundwater temperatures in the lake surrounding are almost constant throughout the year, in the range from 14.6 ℃ to 13.1 ℃, while thermodynamic cycle of the lake conforms to the characteristics of a monomictic, medium depth lake in the moderate climate belt. Present and future climate simulations using three limited area models were analyzed （Aladin, Promes and RegCM3）, they pointed out further air temperature increase in range of 0.27 ℃/10 yrs to 0.32 ℃/10 yrs. The significant changes of precipitation rates were not indicated. Considering increasing water consumption from the lake, already asserted negative trends, indicated climate changes and possible effects on the lake recharge, it is necessary to establish continual monitoring of parameters that describe lake system behaviour and periodically analyze lake conditions, especially with respect to the extraction for the public water supply.