Rivers and Lakes in Languedoc-Roussillon, France
Étang de Thau or Bassin de Thau (dark blue, center) is the largest of a string of lakes that stretch along the Languedoc-Roussillon, the French coast from the Rhône River to the foothills of the Pyrenees which form the border to Spain. It is the second largest lake in France.
Other lakes and swamps can also be seen along the coast to the northeast and southwest. Several rivers spill sediments into the Mediterranean Sea, most notably the Rhône, east of the Étang de Thau, and the Orb and the Aude, west of the Étang.
The Étang de Thau itself is about 21 km long and 8 km wide, with an area of 7,012 hectares. The mean depth of the étang is 4.5m, but in the central navigation channel it can be 10 metres deep.
Until relatively recently the étangs from Marseillan to the Rhône were a continuous stretch of inland waterway. Linked, now, by the Canal du Rhône à Sète to the river Rhône and by the Canal du Midi to Bordeaux via Toulouse, the étang also has access to the Mediterranean at Sète.
To the east, between Balaruc and Sète, the borders of the lagoon are largely industrial. The south bank is formed by the coastal strip from Sète to Cap d’Agde. The northern side has villages dedicated to fishing and the production of shellfish.