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Forests and Water Quality

Trees and forests are one of the best ways to reduce pollutants, sedimentation, and stormwater runoff.

Trees and forests are one of the best ways to reduce pollutants, sedimentation, and stormwater runoff. Leaving stream and river banks as natural as possible — with soil undisturbed and covered with trees and shrubs — can prevent erosion.

Water seems common, but you might be surprised to know just how uncommon it really is. As far as we know, Earth is the only planet in our solar system where water exists as a liquid. No living thing — plant or animal — can survive without it. In fact, water makes up a large percentage of all living things — and the Earth also! Water covers more than two-thirds of the Earth. About 60 percent of the human body is water. And more than 50 percent of a tree is made up of — you guessed it — water!

The water of the Earth’s surface is mainly found in oceans (more than 97 percent) and frozen polar ice caps and glaciers (about 2 percent). Less than one percent of all the surface water on Earth is fresh water that you and I can drink. Because water is necessary for life, it’s important that we keep it clean. A forest plays a big role in maintaining and improving water quality.

What is a Watershed?
Raindrops fall. Some soak into the ground. Some join with other drops and trickle down slopes. The trickles join to form streams. These streams connect to make rivers. Rivers then make their way to the sea. All the land drained by a stream and its branches, or by a river and its streams, is called a watershed. Scientists study watersheds to learn how much water is available to meet people’s needs. The topography — the physical appearance of the land — along with the plants, the soil, the rock formations and the climate, all affect the water in a watershed.

Forests and the Watershed
Heavy rain in a watershed can cause severe flooding, which destroys land and property. Flooding is less likely if a watershed has carefully managed forest areas or wetlands. (Wetlands are places that are flooded or boggy all or part of the year. Forests can be wetlands, too.) Forest soils soak up water. The roots of trees also anchor soil and keep it from washing away — even after the trees are harvested. Wetlands — usually swamps and marshy areas — act as natural sponges, soaking up rain-water that might cause flooding.

Link to US Forest Service website: “Water and Forests: The role trees play in water quality”