It was invented maybe 50 years by the Lebsack brothers here in northern Colorado, and a couple of them farmed our farms for us, so we got to see the invention in action and various stages of evolution.
The ditch water flows through a screen that catches the debris, and a number of push broom heads mounted on pair of chains clean the screen. This is powered by the water flowing through a water wheel, so no electricity is required to install it in a ditch wherever needed.

The Lebsacks have since sold the business to someone outside their family, but the version now being marketed is very recognizable.

We're going to visit my farm sometime this week. It's been very dry up until some good rain last week that was the farmers' delight. It's all about the weather when you're a farmer.