Spain has an important maritime waterway, the Guadalquivir, in the south, used by deep-sea ships up to the port of Sevilla. Small boats can continue up to Cordoba depending on the water level. The most important waterway for boating is the river Ebro, which is being developed for tourism from its mouth in the Mediterranean south of Barcelona to Mequinensa, 160 km inland. The river was navigated even further upstream in the Middle Ages, as the main trade route for the city of Saragossa. It was even planned in the 19th century to make it a large-scale waterway, hence the enormous dimensions of the lock built at Xerta in 1860. However, industrial, hydropower and irrigation requirements soon gained precedence over navigation, and substantial dams were built at Riba-Roja d'Ebre and Flix…