Hydrosphere Notes Parts 6 - Groundwater

Where is most of Earth’s useable freshwater found? ~97% is Groundwater

What is groundwater? The water beneath Earth’s surface in soil pore spaces and cracks in rocks It is usually within 100 meters of Earth’s surface

Why is groundwater important? Parts of the country don't have ample surface- water sources, such as the arid West. It provides about 38 percent of the water delivered by water departments for use in our homes, businesses, and industries Provides drinking water for the 99 percent of the rural population who supply their own water from their own wells. Although only about 19 percent of the Nation's water withdrawals come from ground-water sources, it supplies water in greater amounts than surface water for some uses.

What is PERMEABILITY? Permeability is a measure of a soil's or rock's ability to transmit a fluid, usually water.

What are factors that cause some materials to be more PERMEABLE? The size of pore space and interconnectivity of the spaces help determine permeability, so shape and arrangement of grains play a role. The more mixed the grain sizes, the lower the permeability because the smaller grains fill the openings created by the larger grains.

Which materials have the greatest permeability? Gravel has a high permeability due to the large grain size and how well the pore spaces are connected. Sand has a moderate permeability due to the smaller grain size.

What are factors that cause some materials to be more IMPERMEABLE? Small grain sizes with large surface areas, which results in increased friction. Also these pore spaces are not well connected.

Which materials have the least permeability? Clay has low permeability due to small grain sizes with large surface areas, which results in increased friction. Also these pore spaces are not well connected. Limestone, and other non-porous rocks

What is POROSITY? Refers to the amount of open space in a material. The greater the porosity the greater the ability to hold water

Hydrosphere Notes Parts 7 – Groundwater Simulator

Where does groundwater come from? Water enters the ground in recharge areas as infiltration including rain, melting snow, water in some streams, lakes and wetlands.

Groundwater can move through the ground and into a lake or stream. Water in a lake can soak down into the ground and become groundwater. How does groundwater get below the surface?

How does groundwater move? Water flows downward through permeable soil, sediments until all of the pores are saturated with water. Pressure builds and causes the water to move toward a discharge area at the land surface.

Aquifer An area that holds a lot of water, which can be pumped up with a well, is called an aquifer Good aquifer materials are sand, gravel, or fractured bedrock because they are permeable and porous What are the properties of aquifers?

An area that holds water, but will not allow the water to flow through easily, is called an aquitard. The water cannot be pumped out. Materials such as clay, limestone, or any other non-porous rock make good aquitards Aquitard What are the properties of aquitards?

The area that is filled with water is called the zone of saturation and the top of this zone is called the water table. The layer of earth above the water table is called the zone of aeration. The water infiltrates through this layer as it moves down to the water table. What is the difference between the zone of aeration and the zone of saturation?

The layer of earth above the water table is called the zone of aeration. The water infiltrates through this layer as it moves down to the water table.

Get it? The top of the water is a table! The water table may be very near the ground surface or it may be hundreds of feet deep.

Water pumped from the ground-water system causes the water table to lower and alters the direction of ground- water movement. Periods of drought will also cause the water table to lower. What can cause the water table to change?

What is a cone of depression? When a well is pumped, lowering the water table around the well and causing a cone shaped depression.

Hydrosphere Notes Parts 8 – Groundwater Simulator II

What is a Plume? The distribution of the contaminated groundwater. The boundary of the contamination.

GROUNDWATER CONTAMINATION Most groundwater is clean, but groundwater can become polluted or contaminated.

What is a saltwater intrusion? When pumping of a well near an ocean coastal area draws saltwater into a freshwater aquifer, contaminated it.

How can groundwater become contaminated? It can become polluted from leaky underground tanks that store gasoline, leaky landfills, or when people apply too much fertilizer or pesticides on their fields or lawns. When pollutants leak, spill, or are carelessly dumped on the ground they move through the soil.

How can contaminated groundwater contaminate surface water? Contaminants introduced at the land surface may infiltrate to the water table and flow towards a point of discharge, either the well, stream, or lake.

Why is groundwater contamination a concern? Because it is deep in the ground, groundwater pollution is generally difficult and expensive to clean up.