Possible Clues:

• German river leading, in essence, to Cologne, do we hear?
• It flows into the Szczecin Lagoon
• It forms part of Germany’s eastern border
• This one is in central Europe
• River of eastern Germany
• River forming part of Germany's eastern border
• Szczecin Lagoon feeder
• River through Wroclaw
• About to tackle rising river
• River separating Germany and Poland