Define water pollution, point source pollution, and non-point-source pollution. Which of the two (point source or non-point-source) is easier to identify? Which is easier to legislate? Which currently poses the greatest threat to fresh water?

Water pollution

Define water pollution, point source pollution, and non-point-source pollution. Which of the two (point source or non-point-source) is easier to identify? Which is easier to legislate? Which currently poses the greatest threat to fresh water?