Lake Alexandrina is a large lake about south east of Adelaide, South Australia. The lake covers an area of . The Murray River flows into the north of the lake near Wellington. Water from the lake enters the sea through an opening into Encounter Bay. In 1940 a number of walls were built to stop sea water from flowing back into the lake which would stop the lake from being salty. These walls separate the lake from the Murray River's estuary lagoon, called the Coorong.