E&E 151 S Introductory Geology: Chapters 11.1 - 11.5 (Groundwater Pt. 1) Definitive Study

Groundwater

Water found beneath the surface filling pore spaces in rock and sediment. It accounts for over 98% of all available liquid freshwater (~1.70% of total global water) and is the most extracted natural resource.

Porosity

The percentage of total rock or sediment volume consisting of open pore spaces, measuring fluid storage capacity. (Formula: Porosity = Volume of Voids / Total Volume)

Permeability

The capacity of a material to transmit fluid through interconnected pore spaces (measured as volume per time across a specific area).

Aquifer

A highly permeable and saturated body of rock or sediment that easily yields usable water.

Aquitard / Aquiclude / Confining Unit

A low-permeability or impermeable rock layer that restricts or completely prevents groundwater flow.

Hydraulic Head

The elevation of groundwater combined with the fluid pressure exerted on it at a given point.

Hydraulic Gradient

The slope of the water table. It is calculated as the difference in hydraulic head between two points, divided by the horizontal distance between those points.

Hydraulic Conductivity

A specific numerical measure of permeability applied to a particular aquifer material.

Darcy's Law

A principle stating that groundwater velocity is directly proportional to permeability multiplied by the hydraulic gradient. (To find actual velocity, divide Darcian velocity by rock porosity).

Equipotential Lines

Contours on a map representing points of constant hydraulic head.

Recharge

Water entering the saturated zone.

Discharge

Water leaving the saturated zone.

Stable water level

Discharge = Recharge

Falling water level (depletion)

Discharge > Recharge

Rising water level

Discharge < Recharge