April 25th is National Arbor Day, so what better week to talk about why trees are so important for water quality!
Without trees and other vegetation such as shrubs and grasses, all runoff would go into streams and lakes. Runoff often carries pollutants and dissolved contaminants that can pollute surface water supplies. These pollutants include fertilizers, herbicides, pesticides, nutrients and bacteria from concentrated livestock operations, oils, antifreeze, road salts, and sediment from croplands, urban construction sites and eroding stream banks. Additionally, when water runs off the land quickly instead of allowing some moisture to enter the ground, groundwater supplies cannot recharge.
Strategically planted trees can help alleviate some of the issues associated with runoff and improve water quality. The leaves and branches of a tree can catch rainfall, slowing the movement of rain water. This allows time for the water to soak into the ground and recharge groundwater supplies. The root growth and plant litter help this recharge process by improving the soil structure and enhancing the infiltration of rainwater. The contaminants are also diminished during the recharge process when they are immobilized and transformed by soil microbes or taken up by the trees and other vegetation.
Image credit: acreage.unl.edu
To learn more about how to use trees to improve water quality, take a look at this brochure produced by the USDA National Agroforestry Center or contact the Agroforestry Center at 402.437.5178 ext. 4011.