Rising in the Cantabrian Alps, FTP, name this river that drains the Iberian and Pyrenees Mountains, the longest river entirely within Spain.
It is useless for navigation because tributaries like the Cinca-Segre, Gallego and Jalon Rivers drain different climate zones, causing its volume to vary.  Large hydroelectric plants on this river, like the one south of the Embalse de Mequinenza, supply half of its country's electricity.  Its wide delta forms the Cape of Tortosa and shapes the southern boundary of the Gulf of Saint Jordi.  The province of La Rioja as well as the cities of Tudela and Zaragoza face its banks.  Rising in the Cantabrian Alps, FTP, name this river that drains the Iberian and Pyrenees Mountains, the longest river entirely within Spain.
It is useless for navigation because tributaries like the Cinca-Segre, Gallego and Jalon Rivers drain different climate zones, causing its volume to vary.  
the Ebro