What is headwater, invert, and outlet in a culvert design?

• A. Headwater is downstream water depth; invert is top of culvert; outlet is where water enters.
• B. Headwater is the water depth at the culvert outlet; invert is the bottom inside surface; outlet is where water exits.
• C. Headwater is the water depth at the culvert inlet; invert is the lowest inside bottom of the culvert; outlet is where water exits.
• D. Headwater is upstream water depth; invert is the lowest inside bottom elevation; outlet is where water exits.

Answer: (C)