When rain falls on a building, it lands on a rooftop, drains to the gutters and drainpipes and then is diverted either across land or to storm drain pipes. This rooftop runoff ultimately reaches local waterways. When the rainwater is carried across landscapes, it picks up detrimental pollutants such as bacteria from animal excrement or decaying animals, chemicals, metals, nitrogen and phosphorus from fertilizers, oil, pesticides, sediment and trash. All of these collected surface pollutants contaminate waterways and affect native aquatic plants and animals.
Rainwater harvesting follows ecologically sound principles for water use as it reduces the impact on the land, promotes sustainable practices, reduces storm water runoff, reduces peak flow levels, reduces reliance on ground and surface water, allows for groundwater recharge, and promotes water conservation. Rainwater harvesting, individuals and businesses can divert rooftop runoff into an on-site storage tank or pond, thus preventing it from running across the landscape and further contributing to non-point source pollution. Modern rainwater harvesting systems are 95% efficient at collecting rooftop runoff.
Today’s rainwater harvesting systems have evolved significantly and offer technologically advanced components. However, harvesting rooftop rainwater is more popular in European countries like Germany and England than the United States. Adoption is equally low in most states, with most adopters being rural dwellers with failing wells with no local municipal line and large corporations wishing to conserve water and reduce utility bills.