Water Table: Definition, Depth & Effects

Instructor: Yuanxin (Amy) Yang Alcocer

Amy has a master's degree in secondary education and has taught math at a public charter high school.

In this lesson, you'll learn where in the world you can find a water table. You'll also learn just how important this water table is, and how it can negatively impact a particular area if it changes.

What Is the Water Table?

When you drink a cup of water, do you ever think of where your water comes from? Did you know that most people that don't live near a clean river or lake get their water from the ground? According to the United States Geological Survey, about half of the people that live in the U.S. get their water from the ground, which is called groundwater. Basically, to get groundwater, you have to dig.

When people have to dig to get their water, they'll usually build a well. These wells go deep underground to reach what's called the water table, or the depth at which the ground is saturated with water. When you've reached the water table, the ground underneath is all saturated with water. In order for the well to extract water, the well must be dug so that it reaches below the water table. That way, the saturated ground will release water into the well to be taken up.

How Deep Is It?

The depth of the water table changes depending on where you are and what time of year it is. The United States Geologic Survey also keeps track of the depth of wells around the U.S. The depth of these wells is a good reference for the depth of the water table in these regions, as well. For example, the well depth at Boron in the state of Arizona is 998 feet, while the well depth of a well in Ohio not too far from Fort Wayne, Indiana is only 335 feet.

There's no standard when it comes to well depth. These same wells can have different depths depending on the time of year. If it's the dry season, then the well depth of these same wells may be deeper, and during an extremely rainy wet season, the well depth of these same wells may be higher and not so deep.

How Does It Change?

What accounts for the changes in the water table? Location has a lot to do with the depth of the water table. If the area is really close to a beach, then the water table is usually very close to the water level at the beach. Factors that can make the water table rise going further away from the shore can be soil that's good at absorbing and keeping water, along with trees and other plants that pull water up with their roots.

Other factors also play a role here, though. For example, areas that receive a lot of regular rainfall will have a water table that's closer to the surface than an area that doesn't receive a lot of rainfall. In deserts, the water table may be so deep in the ground that it wouldn't make sense to make a well, if it's even possible to dig that deep!

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