That's the third time Dean has mentioned the reservoir in one day.

He slows his chewing, swallows his mouthful of food and sets the burger down on the table. Crossing the room, stopping at the foot of Dean's bed and tucking his hands into the pockets of his jacket, Cas watches Dean with that sad, tired, anciently-old look in his eyes. One that tells of a thing that's watched civilizations fall, watched millions die in wars and of disease and still can't think of anything more unfair than Dean suffering hardship.