Like good neighbours, trees and water help each other to prosper. Listen to the stories of your grandparents. They may say, “When we were children there were forests and trees all around, and there were cool springs of water that flowed from the hillsides or trickled into the rivers. We always said that spring water was the sweetest to drink. But then the trees began to disappear. People cut down the trees, and did not replant them. The fresh water springs also disappeared, and now there is a water shortage.”
Today let’s find out how trees keep water in our soil and protect springs.
Tree roots are important When you look at a tree you see a trunk and, above it, branches and leaves. If you were able to dig out an entire tree, you would see that the part of the tree that is underground the root system looks like an upside down tree!
The roots of a tree spread deeply and widely in the soil. If you look at the large roots you can see they have many smaller roots and hairs attached to them. These are called rootlets and roothairs.
How trees help to store water Trees affect the way water moves into and through the soil in a number of ways. As tree roots grow they make large channels for water to move through. Tree branches and leaves stop raindrops from hitting the ground too fast so the soil has more time to absorb the rain water. Less water will run off the surface and that will reduce soil erosion. Trees provide shade so that less water evaporates from the soil. This is particularly important in hot, dry areas.
As more rain falls, water moves deeper into the soil. Eventually, the flow of water may be stopped by a hard layer of soil or rock. At this point the water will flow along the easiest path, generally flowing to a lower place. Often, this water will end up in a spring, flowing out the side of a hill or gathering in a pond at the bottom of a slope. Sometimes the water will move very deep into the soil and can only be reached by digging a well.
Spring water is fresh and tastes clean. The soil acts as a filter and removes organisms that can cause disease and bad tastes and smells. Spring water is usually cleaner and healthier to drink than water from dams and shallow, hand dug wells. However, even spring water can be contaminated by wastes from industry and agriculture.
If you protect trees you protect springs Communities with a water shortage should answer some important questions. What is happening to the rainwater? Are there enough trees to protect the water in the soil, or are the trees quickly disappearing?
Just as your grandparents explained, when there are not many trees, there are often water shortages. Rainwater will not stay in the soil, especially in hot areas. It will evaporate quickly into the air or it will move along the soil surface carrying away the topsoil. The soil will become poor and infertile.
Even if this has already happened in your community, planting trees this season will help to reduce some of these problems.
You can also protect trees that are already growing. It may take many years for a tree to reach a mature size where the benefits to the soil and groundwater will be the greatest. Don’t allow animals to eat the branches on or to rub against young trees. Remember, if the top of the tree dies, the roots of the tree may also die. Then the tree roots will not be able to hold water in the soil, and fresh water springs will dry up.
If you protect trees and springs, your community will have a continuous supply of clean water.
This script was prepared by Helen Hambly Odame, Agroforestry Researcher, Eastern and Southern Africa Regional Office, International Development Research Centre, P.O. Box 62480, Nairobi, Kenya. Jamie Simson, Department of Environmental Biology, University of Guelph reviewed this script.
This script is based on two scripts, called Trees, Terraces and Bulldozers and Trees (No. 46 and No. 92), from the “Doctor AMREF” radio series, AMREF (African Medical Relief Foundation), P.O. Box 30125, Nairobi, Kenya.