Chap+17+Groundwater+F20 (copy)

Groundwater

Water stored beneath Earth’s surface in pores and fractures in rocks.

Hydrogeology

The study of groundwater.

Pores

Spaces between grains in a rock.

Fractures

Open cracks in rock.

96% of Freshwater

Groundwater is the largest source of freshwater available to humans, accounting for 96% of all liquid freshwater.

Ice sheets and glaciers

Hold 68.7% of freshwater.

Lakes

Hold 1.2% of freshwater.

Soil moisture

Accounts for 0.294% of liquid freshwater.

Rivers

Make up 0.004% of freshwater.

Water vapor

Accounts for 0.049% of freshwater.

Fresh Water Volume - Ice sheets and glaciers

24,000,000 km³, which represents 84.945% of the total fresh water.

Fresh Water Volume - Groundwater

4,000,000 km³, representing 14.158% of total fresh water.

Porosity

The amount of void space in rock.

Permeability

The ability of rock to transmit water.

Vesicular basalt

A rock with high porosity but very low permeability due to unconnected pores.

Uncemented Sandstone

Has high porosity and permeability.

Cemented Sandstone

High porosity but low permeability due to cement blocking pathways.

Aquifer

Permeable rock strata that transmit groundwater freely.

Aquitard

Impermeable layer preventing water movement.

Groundwater Recharge

Occurs when rainwater infiltrates into the ground.

Wetlands

Enhance groundwater recharge but are decreasing due to development.

Soil Moisture

The shallow surface layer wet by rain.

Zone of Aeration

Space between surface and water table containing both air and water.

Water Table

Top of saturated zone where groundwater begins.

Zone of Saturation

Area entirely filled with water.

Water Table Dynamics

The shape of the water table mimics the ground surface and levels fluctuate based on rainfall.

Unconfined Aquifer

An aquifer that is exposed to the surface.

Confined Aquifer

An aquifer sealed by impermeable layers.

Artesian Pressure

Water rises above the aquifer when punctured by a well.

Darcy’s Law

Describes groundwater discharge (Q) in relation to hydraulic conductivity, area, and hydraulic gradient.

Volume of Water Flow (Q)

The amount of water flowing through a given area.

Cone of Depression

Drawdown area around a pumping well that can affect nearby wells.

Nonrenewable Resource

Groundwater which is over-extracted exceeding recharge rates.

Subsidence

Ground sinking due to excessive water removal.

Saltwater Intrusion

Occurs at coastal wells when freshwater is over-pumped.

Springs

Natural flows of groundwater where water table meets the surface.

Geysers

Intermittent springs where columns of boiling water erupt.

Hot Springs

Water that is 6ºC to 9ºC warmer than ambient temperature.

Groundwater Contamination

Pollution of groundwater from sources like sewage and industrial waste.

Karst Landscapes

Formed by groundwater erosion, characterized by sinkholes and disappearing streams.

Sinkholes

Collapse of cave roofs creating depressions in the ground.

Sinking Streams

Streams that disappear underground into sinkholes.