Ria Formosa is a large coastal lagoon, with an area of more than 80 Km2 located in southern Portugal close to the cities Faro and Olhão (see Figure 1). Its composition is characterised mainly by mudflats crossed by a complex network of channels. At low waters more than 80% of the area is dry, while in high waters most of the mudflats are submerged. The average depth is thus very low (less than 1 meter) but the main channels have depths of about 5 meters.
The lagoon is protected from the sea by a set of five barrier islands and two peninsulas. Six bars make the connection to the sea. These are highly dynamic inlets with a regular migration to East. Ria Formosa doesn’t have permanent fresh water streams discharging into it. During rain events some small rivers can present important instantaneous water flows but for the annual average situation its importance is small.
Figure 1 - Ria Formosa.