A rain garden is a garden strategically located and designed with the purpose of retaining and filtering runoff water from roofs, lawns, and streets. Run off water is full of toxins ranging from pesticides, fertilizers, oil and other chemicals left on the street by cars and humans. This water can be very harmful to the ecosystem, and reduces drinking water quality. According to researchers at the University of Connecticut "a shallow depression in a garden containing bark mulch and shrubs can remove up to 99% of toxins." Although this might not seem like a substantial difference in the larger scheme, rain gardens are scientifically proven affective.