Review - The Hydrosphere

• Scientists classify Earth's water to make it easier to study.

• Oceans are liquid saltwater, and compose 97% of Earth's water.

• Glaciers are frozen freshwater and compose 2% of Earth's water.

• Accessible Water is the water humans use to meet their needs. It is liquid freshwater, and composes 1% of Earth's water.

What is Groundwater?

• Scientists classify Earth's liquid freshwater into "Surface Water" like Lakes, Rivers, and Ponds or "Groundwater," which is the water underground.

• Groundwater is not like a river or lake underground.

• Instead, it is water settled into spaces between rocks and dirt.

Measuring Groundwater

• Scientists measure the amount of groundwater by tracking the location of the "Water Table."

• Under the water table, the rock layer is full of water.

• Above the water table, there is much less water.

• A high water table means lots of water is accessible for humans.

• A low water table means less water is accessible.

Accessing Groundwater

• To access groundwater in the humans need to dig a hole.

• This hole is called a "Well."

• If the water table is above the well, humans can access the water.

• If the water table is below the well, the well will run dry.

• When the water table is too low for people to meet their needs, the area is said to have a "drought."

Refilling Groundwater

• Refilling Groundwater is part of the water cycle.

• Most groundwater started as precipitation.

• Groundwater is pulled down toward's Earth's center by gravity.

• It is stopped by rocks that are too dense to pass through.

• This dense rock is called "Bedrock."

Protecting Our Groundwater

• We need our groundwater to drink and to irrigate crops, so it is important for our groundwater to stay clean.

• Any pollution in Earth's surface water will also be pulled by gravity into our groundwater.

• This includes garbage from landfills, fertilizers from farms, and human waste from septic tanks.

• Restrictions on pollution can keep our groundwater safe for people to use.