The worldwide event, the Dow Live Earth Run for Water, is on this month in LA.
Kara Goucher, Carl Lewis, and Jenny Fletcher will run in the events and Melissa Etheridge will play the LA concert.
Jessica Biel, Alexandra Cousteau, Pete Wentz, and Angelique Kidjo are just some of the charitys supporters.
Run or walk 6km to help highlight the scarcity of water for people in developing countries.
The Dow Live Earth Run for Water is on 18 April.