Alumna Annie Graefe ’11 talks about trees and water quality.
Agnes Scott Hall, behind you, straddles the Eastern Continental Divide. Rainfall here makes its way via the Chattahoochee basin to the Gulf of Mexico; on the opposite side of the building, the south-facing side, it travels via the Ocmulgee basin to the Atlantic Ocean. In whatever direction it flows, that water is cleaner than it would be otherwise, courtesy of more than 1750 trees growing on Agnes Scott’s campus.
As a key part of the water cycle, Agnes Scott’s trees improve water quality by reducing stormwater runoff, which carries dirt, chemicals, and other pollutants into our streams and rivers. First, leaves and branches intercept some rainfall. The water then evaporates or drips to the ground with less impact and runoff. Second, fallen leaves and twigs add organic matter to the soil, enabling it to absorb more rainfall. Finally, some of the water enters the tree through the roots and exits via leaves in a process called transpiration.
Red maples (Acer rubrum, left of the path) are widely planted in towns and cities. Their roots can penetrate and loosen compacted soil, improving its infiltration rate. Some of the water filtered by the campus’s approximately 120 maple trees makes its way to Lake Agnes, the college’s retention pond. This pond supplies water to irrigate these very same trees, which convert the water to sap, feeding birds, butterflies, ants, and other wildlife!