Trespass grows threaten creeks like this one in Prairie Creek Redwoods State Park, Cali. Growing cannabis requires enormous amounts of water. Water illegally stolen from creeks such as this. What isn't stolen is often polluted. Mourad and Greta as well as collaborating scientists with the U.S. Forest Service have been testing streams only to find them testing positive for an array of pesticides, fertilizers and other chemicals found out at grows.