Honolulu Mayor Peter Carlisle is urging residents to reduce their use of water and energy to help the city in a national contest.

The Mayor’s Challenge for Water Conservation runs through April 30.

Participants can win prizes including a Toyota Prius car, and environmentally friendly showerheads. 

Board of Water Supply Manager and Chief Engineer Ernest Lau said Monday the contest will help demonstrate the collective impact of each person’s water-reducing efforts.

The contest is nonprofit competition founded by The Wyland Foundation.