Brook vs. Creek vs. Stream vs. River

As I was reading today I wondered what the difference is between a brook and a creek. Then I got to wondering about the stream and the river.

Dictionary.com defines them as...

Brook - a small, natural stream of fresh water

Creek - (in the U.S., Canada, and Australia.) a stream smaller than a river

Stream - a body of water flowing in a channel or watercourse, as a river, rivulet, or brook

River - a natural stream of water of fairly large size flowing in a definite course or channel or series of diverging and converging channels

So a brook is smaller than a creek which is smaller than a steam which is smaller than a river. I'm just trying to decide if my grandpa's farm has a creek or a stream or a brook that runs along one side. It must be a creek considering it doesn't look nearly as lovely as the description sounds of the brook that streams by Green Gables.