How does Hans save Axel and the Professor in chapter 23?

Hans discovered an unleashed a stream of water. Thus, the parched men who'd been without water were satiated. 

I was stirred up with excitement. I hardly dared guess what the hunter was about to do. But I could not but understand, and applaudan d cheer him on, when I saw him lay hold of the pickaxe to make an attack upon the rock.

"We are saved!" I cried.

"Yes," cried my uncle, almost frantic with excitement. "Hans is right. Capital fellow! Who but he would have thought of it?"