National Groundwater Awareness Week

03/09/2020

Groundwater is found in the spaces between particles and cracks in the underground rock in formations known as aquifers.

Even though it is out of sight, groundwater should not be far out of mind and March 8 – 14, is National Groundwater Awareness Week.

In Texas, groundwater provides 62% of all freshwater used, supplies 76% of the water used by agriculture, and is a source of drinking water (from both public and private wells) for over 6.7 million Texans.

Groundwater 101

Water is always in motion. When rain falls to the ground, some of it flows along the surface to streams or lakes, some of it is used by plants, some evaporates and returns to the atmosphere, and some sinks into the ground. Where does the water go then?

Imagine pouring a glass of water onto a pile of sand. The water moves into the spaces between the particles of sand. This is groundwater.

Groundwater is used for drinking water by more than 50 percent of the people in the United States, including almost everyone who lives in rural areas.

The U.S. Geological Survey estimated that in Texas, approximately 29 percent of the population used groundwater as a drinking water source in 2015.

According to the 2017 State Water Plan developed by the Texas Water Development Board, groundwater supplied 62 percent of the 13.7 million acre-feet of water used in Texas in 2014.

Farmers use about 76 percent of this groundwater to irrigate crops.

Approximately 18 percent of the water used for municipal needs was groundwater. Most of the western half of the State and a good part of the eastern half of the State rely primarily on groundwater resources.

Groundwater is stored in–and moves slowly through–layers of sand and rock called aquifers.

Aquifers typically consist of gravel, sand, sandstone, or fractured rock, like limestone and granite. These materials are permeable because they have connected spaces that allow water to flow through.

The speed at which groundwater flows depends on the size of the spaces in the soil or rock and how well these spaces are connected.

Groundwater can be found almost everywhere. The area where water fills the aquifer is called the saturated zone (or saturation zone). The top of this zone is called the water table.

The water table may be located only a foot below the ground’s surface or it can be hundreds of feet down. It can rise or fall depending on many factors.

Heavy rains or melting snow may cause the water table to rise, or heavy pumping or drought may cause the water table to fall.

Water in aquifers may be brought to the surface naturally through a spring and can be discharged into lakes and streams.

Groundwater can also be extracted through a well drilled into the aquifer. All of these cause groundwater to interact with the other waters of the hydrologic cycle.

Groundwater supplies are replenished, or recharged, by rain, snowmelt, or runoff moving through the overlying layers of soil and seeping into the aquifer below.

In some areas of the world, people face serious water shortages because groundwater is used faster than it is naturally replenished. Groundwater may also be polluted by human activities.