Vistula Lagoon million. However, major ecological considerations stand in the way. For example, mammal migration along the lagoon could be disrupted. Also, the inflow of brackish waters from the Baltic sea could result in serious unbalancing of the lagoon's freshwater ecosystem. From 1772 until 1918, the lagoon was part of the Kingdom of Prussia, which had become part of the German Empire in 1871. Between 1920 and 1946 it was split between Germany and the Free City of Danzig. At present state since 1945 its eastern part belongs to Russia (formerly USSR), Poland has 43.8% of its area at lagoon's western side.
Koggala Lagoon streams, Mudiyansege-ela stream and Thithagalla-ela stream, is the second largest freshwater inflow. Heen-ela stream contributes a minor to the freshwater inflow In addition to above four streams, Kahanda-ela stream, Gurukanda-ela stream and Thelambu-ela stream are also contributors for freshwater inflows but are presently abandoned with overgrown vegetation. The only outlet of the lagoon is Pol-oya located at the southeast corner; a narrow long canal, which connects the lagoon with the Indian Ocean. The lagoon has a hydro-catchment area of approximately . Various land use practices exist in the catchment, which mainly includes small-scale fishing industry and paddy farming. The Koggala