Influence of water levels of Vrana Lake and the Adriatic Sea to the water chemistry of Vrana lake

The set objective of this field research was the determination of anomalous states in the Vrana Lake waters that might be the consequence of environmental pressure. We postulated that water quality in Vrana Lake Nature Park would be mainly influenced by the agriculture and impact of the sea and climate. Methods employed include analysis of dynamics of temperature and precipitation, sea water and lake water levels and water monitoring in a time period from January 2000 to December 2009. Adriatic Sea and Vrana Lake water levels were monitored at water gauges placed at two sites. Water sampling was carried out at two measuring points as a part of the national water monitoring program. Comparison of water fluctuation levels in the lake and the sea with concentration dynamics of calcium, magnesium, chloride and sulfate ions, reveals that the relationship between lake water levels and sea water levels has a powerful and direct impact on the chemical activity of the lake water. The alkalinity and high electro conductivity of lake water is the consequence of mixing process with seawater. Penetration of sea water into the lake corresponds with the duration and intensity of the dry periods. Data on lake water hardness in location Prosika follows the same trend as data regarding ions and electro conductivity at the same location. Since our data indicates that with the change in the lake water and the sea water levels, the salinity of the lake changes, we conclude that sea water is the major source of salt in the lake.