Ardèche is a tributary of the river that has a mouth at what body of water?
Rhône The Rhône ( ; French: "Le Rhône" ] ; German: "Rhone" ] ; Walliser German: "Rotten" ; Italian: "Rodano" ] ; Arpitan: "Rôno" ] ; Occitan: "Ròse" ] ) is one of the major rivers of Europe and has twice the average discharge of the Loire (which is the longest French river), rising in the Rhône Glacier in the Swiss Alps at the far eastern end of the Swiss canton of Valais, passing through Lake Geneva and running through southeastern France. At Arles, near its mouth on the Mediterranean Sea, the river divides into two branches, known as the Great Rhône (French: "Le Grand Rhône") and the Little Rhône ("Le Petit Rhône"). The resulting delta constitutes the Camargue region.
Caia (river) The Caia is a river in the Iberian Peninsula, a tributary to the Guadiana. It is one of the main water courses in the Portalegre District, Portugal. Portugal does not recognise the border between the Caia and Ribeira de Cuncos River deltas, since the beginning of the 1801 occupation of Olivenza by Spain. This territory, though under "de facto" Spanish occupation, remains a "de jure" part of Portugal, consequently no border is henceforth recognised in this area.