Third and fourth-graders learned about the importance of keeping the San Antonio River clean this week with a lesson from the San Antonio River Authority.

During the presentation, students experienced a scale model of the river.

They used cinnamon and water to see how pollution flows down its headwaters just north of downtown, through San Antonio and continuing south 240 miles until it almost reaches San Antonio Bay.

And what kinds of things pollute the river? Trash, petroleum products, and animal poop (from pets and livestock), for starters. So if you’re a parents of one of these students, expect more awareness of the river in your house.