Saltwater Intrusion of Coastal Karstic Aquifer on the Example of the Boljkovac Water Supply Pumping Station near Zadar, Croatia

Numerous coastal karst springs of the Mediterranean region have problems with salinization. Salinization usually occurs during summer dry periods as a result of long droughts and excessive pumping for water supply. The Boljkovac water supply pumping station has slightly increased parameters that indicate the possibility of salinization during the dry summer periods, but the main salinization occurs post heavy rains which appear after long dry periods in the fall, winter, and spring. Due to the occasional occurrence of salinization, continuous monitoring of the aquifer by depth was set up at the piezometric well drilled near the water supply pumping station. The results of the monitoring were analyzed in relation to external factors that can negatively affect the disruption of the labile dynamic balance of salt and fresh water. The analyzed external factors are the pumping rate for the water supply, the amount of precipitation, surface flow and the interaction of surface water and groundwater, as well as the sea level changes. In Croatia, and the wider Mediterranean area, there are a large number of springs and water wells that have the same or similar problems, so the results of this analysis can be used in designing monitoring and setting up management systems for these coastal aquifers.