Lake St. Lucia

Lake St Lucia
Hippos resting on the shores of Lake St Lucia.
LocationKwaZulu-Natal, South Africa
Coordinates28°00′S 32°25′E / 28.000°S 32.417°E / -28.000; 32.417
TypeEstuarine lake
Primary inflowsMkuze River, Hluhluwe River, Nyalazi River, Mzinene River, Mpate River
Primary outflowsSt Lucia Estuary
Catchment area6,150 km2 (2,370 sq mi)
Basin countriesSouth Africa
Managing agencyiSimangaliso Authority
Max. length60 km (37 mi)
Max. width1–23 km (0.62–14.29 mi)
Surface area325–350 km2 (125–135 sq mi)
Average depth0.9 m (3.0 ft)
Max. depth3 m (9.8 ft)
Surface elevation0 m (0 ft)
Sections/sub-basinsSouth Lake, North Lake, False Bay, The Narrows
SettlementsSt Lucia
Official nameSt Lucia System
Designated2 October 1986
Reference no.345
Official nameiSimangaliso Wetland Park
DesignatedDecember 1999
Interactive map of Lake St Lucia

Lake St Lucia (also Lake Saint Lucia) is an estuarine lake system in northern KwaZulu-Natal, South Africa. It is the largest estuarine lake in Africa and in Southern Africa, covering an area of approximately 325–350 km2 (125–135 sq mi) and accounting for roughly 80% of KwaZulu-Natal's total estuarine area. The lake forms the central feature of the iSimangaliso Wetland Park, South Africa's first UNESCO World Heritage Site, which was inscribed in December 1999, and it has been designated a Ramsar Wetland of International Importance since 1986.

The lake system is noted for its extreme environmental variability. Salinity levels fluctuate from near-freshwater conditions to more than 200 parts per thousand (ppt), nearly six times the salinity of seawater, making Lake St Lucia a global reference system for estuarine research. More then 60 years of peer-reviewed scientific research culminated in the 2013 Cambridge University Press monograph Ecology and Conservation of Estuarine Ecosystems: Lake St Lucia as a Global Model.