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.
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