Rain or snow falling on parking lots, farm fields, streets, industrial sites, and other areas picks up and transports a number of such as soil, fertilizers, pathogens, and chemicals. remove nutrients such as nitrogen and phosphorous from water and tie them up so they are no longer available to pollute the water—thus resulting in cleaner water. Water that moves in channels such as streams or in sheet flow across fields will slow down when they enter wetlands due to increased with vegetation and often due to a lower gradient than the stream or surrounding landscape itself. A variety of that live in wetlands can further change certain nutrients and harmful chemicals into less harmful chemicals, remove the chemicals from the water, and bind them in the sediments. The high production of some wetland hydrophytes further help to remove many excess nutrients from the water and allows them to be stored in the once the plants die.