Groundwater

Groundwater
Some of the water that falls to Earth as precipitation soaks into the ground. Gravity
causes water to seep into the cracks or the spaces between grains in rocks and soils
called pores. In some areas, groundwater is very close to the surface and keeps the soil
wet. In other areas, especially in deserts and other dry climates, groundwater is
hundreds of meters below the surface. Groundwater eventually returns to the surface
and reenters the water cycle. It is an important source of water for many streams, lakes,
and wetlands.
Water Table
Near Earth’s surface, the pores contain a mixture of air and water. This region is called
the unsaturated zone. It is called unsaturated because the pores are not completely filled
with water. Farther beneath the surface, the pores are completely filled with water. This
region is called the saturated zone. The upper limit of the saturated zone is called the
water table.

Wells
People often bring groundwater to Earth's surface by drilling wells. Wells are usually
dilled into an aquifer—an area of permeable sediment or rock that holds significant
amounts of water. Permeability is a measure of the ability of fluid to move through a
porous material. Groundwater then flows into the well from the aquifer and is pumped to
the surface where it can be collected for use by humans. Wells are very important for
people who do not have access to surface water.
Precipitation
Rain, snow, sleet, and hail help to replace groundwater drawn out of wells. When rain
falls or snow melts, some water runs off over land and collects in streams, while some
infiltrates into the pores or cracks of the soil and rocks. During a drought, less
groundwater is replaced, so the water level in a well drops. The same thing happens if
water is removed from a well faster than it is replaced. If the water level drops too low, a
well runs dry.
Springs
A spring forms where the water table rises to Earth's surface. Some springs reach Earth's
surface only after heavy rain or snowmelt. Springs fed by large aquifers flow

Human Influences on Groundwater
As you read, it is apparent how human activity affects surface water. Humans have
influences on groundwater as well. The water beneath Earth’s surface is much more
plentiful than the freshwater in lakes and streams. Groundwater is also an important
source of water for many streams, lakes, and wetlands. 

Some plant species absorb groundwater through long roots that grow deep
underground. People in many areas of the world rely on groundwater for their water
supply. Sixty percent of the water used in Texas is groundwater. Because groundwater is
so important, it is essential to understand the harmful and beneficial influences of human
activity on groundwater.

Pollution
Groundwater pollution is a serious problem. If polluted surface water seeps into the
ground, it can pollute the groundwater below it. Pollutants include pesticides, fertilizers,
sewage, industrial waste, and salt used to melt ice on highways. Acidic runoff from mines
can contain metals. These metals can contaminate groundwater drinking supplies. Urban
runoff from lawns, vehicles, and waste can contain harmful substances that reduce the
quality of groundwater. Pollutants can travel through the ground and into aquifers that
supply wells. People’s health can be harmed if they drink contaminated water.

Aquifer Depletion
The water in an aquifer supports the rocks and soil above it. Precipitation helps replace
groundwater drawn out of wells. During a drought, less groundwater is replaced, so the
water level in a well drops. The same thing happens if water is removed from a well
faster than it is replaced. If the water level drops too low, a well runs dry.

The water in an aquifer supports the rocks and soil above it. In some parts of the world, water is being removed from aquifers faster than it can be replaced. Removing water causes rocks, soils, and sediment to contract. The ground sinks in a process known as land subsidence. This can cause damage to buildings and roads. In coastal areas, land subsidence leads to higher sea levels and increased flood risk. In coastal areas, aquifer depletion can lead to the migration of salty water into aquifers that once held freshwater. Depletion of groundwater can also lower lake and stream levels.

Urban Development
There are multiple environmental impacts related to urban development. Many
communities use underground water supplies for drinking. Covering land with roads,
sidewalks, and parking lots reduces the amount of rainwater that soaks into the ground
to refill, or recharge, underground water supplies.

Conservation
There are many ways that humans can benefit groundwater resources. Managed aquifer
recharge is a way that humans can replenish groundwater that has been used. Surface
water can be redirected across the land surface through canals, infiltration basins, or
ponds or by injecting water directly underground through injection wells. In addition,
using bricks, stones, or gravel for walkways or driveways allows rainwater to soak into
the ground through spaces, replenishing groundwater.

Human Influences on Both
As you just read, many of the same human activities impact both surface water and
groundwater. Just as runoff flows downhill across Earth’s surface, groundwater flows
downhill beneath Earth’s surface. Groundwater flows from higher elevations to lower
elevations. In low-lying areas at Earth's surface, groundwater might eventually seep out
of the ground and into a stream, lake, or wetland. In this way, groundwater can become
surface water. Likewise, surface water can seep into the ground and become
groundwater. Because surface water and groundwater are intertwined, humans can have
a beneficial and harmful influence on both through the same actions. That is why it is
important to protect surface water and groundwater.

Texas Groundwater: A Precious Resource
All humans depend on freshwater for life. We need clean water to drink and grow the
food that we eat. As the second most populated state in the United States, Texas has a
large and increasing demand for freshwater. In addition, the semiarid climate of Texas
leaves the state prone to droughts. Groundwater is an important and limited resource in
Texas, so it is important to understand both the beneficial and harmful influences that
humans have on it.

Texas Aquifers
Groundwater in Texas is stored in 9 major aquifers and 22 smaller minor aquifers. Nearly 80 percent of Texas groundwater is used to irrigate crops. The groundwater stored in these Texas aquifers provides about 60 percent of the state's water supply.

Conservation
1n 1985, the city of El Paso developed Texas's first aquifer recharge facility. Wastewater is treated to the standard of drinking water at the Fred Hervey Reclamation Plant and is pumped into infiltration ponds. At this facility, the treated water is able to seep into the ground to recharge the Hueco Bolson aquifer.

Since 1985, the plant has returned nearly 30 billion gallons of water to the aquifer. Water
treated at the Fred Hervey Reclamation Plant is also sent to irrigation and industrial facilities, reducing the amount of water pumped from the aquifer or diverted from the Rio
Grande.