Hydrology for beginners

That water over there beyond the green is the River Cherwell. It’s carried a whole lot of botanic debris down to the confluence with the River Thames but the stronger flow in the Thames, even disrupted by rain and passing boats, is not letting the water of the Cherwell in. Without the water-dammed detritus I'd never know that.

There are quite a lot of things I’d have been happy studying and hydrology’s one of them.