Water Exchange of Nontidal Estuarine Coastal Vistula Lagoon with the Baltic Sea

Abstract

The objective of the study is to present the main morphometric features of the inner sand bar of the nontidal Vistula Lagoon, to obtain actual data on the water exchange of the lagoon with the Baltic Sea, to compare the time variability of water exchange and regime-forming factors, and to estimate the volume of water exchange. The erosion was revealed for the inner sandy bar (comparing 2012 and 2019) which could be caused by regular dredging of the navigable canal (uptake the marine sediments feeding the bar). A sea-level rise of different origins guides impulse-fold inflow–outflow exchange of the lagoon with the sea estimated by direct current measurements in winter and spring. An inflow–outflow event is sustainable when the water level rises higher than 0.8 cm/h. Spring river input provides the shift in the equilibrium in water exchange toward outflow (by 10% in duration). The average rate of the inflow–outflow is 3.14 and 3.16; the maximum is 8.00 and 8.31 million m3 per hour. The average volumes per inflow–outflow events are 37 and 31 million m3. A simplified formula for calculating the exchange volume based on sea-level changes was recommended using a high correlation between them.