Reader warning: This post is not about water advocacy or rights. Nope…
Today we’ll get a bit scientific. This is about water movement on land.
I have always known the importance of vegetation in reducing soil erosion and siltation in water bodies, but a week ago, in a hydrology class, after 4 years of university education and 5 years of work experience, I finally really understoooooood the science behind the importance of vegetation/soil cover.
I’ll use a head full of hair versus a bald head. Assuming that both have pores that absorb water when in contact. Because of the hair, the head full of hair will slow down the movement of water which will be absorbed by the pores (infiltration)… Okay I think I’ll just use soil because…I’ll just use soil.
So we have soil that has cover, it could be grass, trees, foliage (dead leaves) vs soil that is bare or soil that is compacted/hard because of activities such as overgrazing (too many cows in one area…yes, this can be a problem). When it rains on soil with cover, the water is slowed down by the vegetation and takes its time to get into the soil pore.We call this infiltration– Movement of water from the soil’s surface into the soil pores. So because the water moving on the surface has been slowed down by the vegetation, there are fewer instances of soil erosion (washing away of the top layer of soil which is super important for production of food).
However, when the soil is bare,the rainwater lands on the soil, soil particles jump in surprise and land in areas where the water could have had a chance to infiltrate into the soil. These entry ways are blocked by the surprised soil particles.Because the moving water has nothing to slow it down, it simply runs (runoff) over the soil, carrying alot of soil with it. This soil sometimes ends up in water bodies making the water look browish… We call this siltation. This more often than not reduces water quality and quantity. We’ll discuss water quality and quantity some day soon.
I hope you have more clarity on why vegetation cover is important. For more on this, see the fun video below: