In this topic you will learn about the fresh water found in groundwater.

Soil is the top part of the ground. It is made up of small rock particles, decaying plant and animal materials, water, and air. There are tiny spaces between the particles called pore spaces. These spaces allow liquids and gases to pass through. Materials with pores are said to be porous.

Soil is porous, so water can soak into it. Water in the soil is called soil water. Water passes through the soil and into the porous rocks below until it reaches a layer of nonporous rock. When it can go no deeper, the water begins to fill the spaces in the rocks above. Water in the underground rocks is called groundwater. The upper area of groundwater is known as the water table.

Precipitation that does not evaporate or soak into the ground becomes runoff. Runoff is the water that flows over Earth's surface. The amount and size of runoff is greater at some times of the year, such as during seasons of heavy rains. Soil type and plant life affect runoff. So does the slope of the surface.

Groundwater is an important source of fresh water. Digging a well is a common way of getting water from the ground. For a well to produce water, its bottom must be below the water table. In some wells, pumps bring water to the surface. In other wells water rises on its own because of pressure in underground rocks.

Plants help move water from the soil into the atmosphere. Through their roots plants soak up water from the soil. The water moves to all the plant's cells. Some of the water that isn't used to make food escapes through the plant's leaves. This process is called transpiration.

When there is no precipitation, a drought may occur. A drought is a long period of time with little or no precipitation. Droughts often affect water supplies. Crops and other plants may die during a drought.

Floods are great flows of water over land. This usually occurs because water accumulates faster than the soil can absorb. Floods are dangerous and cause a lot of damage. People build dams and raise river banks in an attempt to control floods.

Fresh water is important for all living things. Understanding how water flows through and above the ground can help in every day activities.