1. She’s walking down the steps.

 

(note: the word "steps" is preferred over "stairs" in this case because the location is outside.)

woman walking down steps

 2. They’re canoeing down the river.

canoe

 3. The train is coming down the track.

train

 4. Water is flowing down the side of a cliff.

(This is a waterfall.)

waterfall
 5. She’s sliding down the railing on her skateboard.
 girl

 6. Don’t let your money go down the drain.

(down the drain: water goes down the drain, but when it’s money, that means you are wasting your money or you are not spending it wisely.)

money

 7. The buffalo is lying down in the dirt.

buffalo

 8. These children are lying down in the snow.

children
 9. He’s upside down.
upside down
 10. So is he. This monkey is hanging upside down.
upside down