The Garonne is a river that flows in southwest France and northern Spain. It flows from the central Spanish Pyrenees to the Gironde estuary at the French port of Bordeaux – a length of 529 km, of which 47 km is in Spain ; the total length extends to 602 km if one includes the Gironde estuary between the river and the sea. Its basin area is 56,000 km², which inc…The Garonne is a river that flows in southwest France and northern Spain. It flows from the central Spanish Pyrenees to the Gironde estuary at the French port of Bordeaux – a length of 529 km, of which 47 km is in Spain ; the total length extends to 602 km if one includes the Gironde estuary between the river and the sea. Its basin area is 56,000 km², which increases to 84,811 km² if the Dordogne River, which flows from the east and joins the Garonne at Bec d'Ambès to form the Gironde estuary, is included.