National Water Act Definition
A partially or fully enclosed body of water, which is open to the sea permanently or periodically, and within which the sea water can be diluted, to an extent that is measurable, with fresh water drained from the land.
[Source: National Water Act (Act No. 36 of 1998)].
Description
Estuaries are the interface between rivers and the sea.
Why are estuaries important?
Both surface and groundwater discharges to estuaries and the sea. The role and importance of groundwater discharge into estuaries is not well understood.
Source: http://www.penmarlampark.co.uk