Possible Clues:

• River flowing through the Broads
• River that drains the western Pyrenees
• River from Cantabria to Catalonia
• Aragon divider
• Spanish runner featuring in outside broadcast
• River that runs through 23-Across
• Longest river entirely within Spanish borders
• Second-longest river in Iberia
• River that rises in the Cantabrian Mountains
• River flowing through Zaragoza, Spain