Chapter 14: Groundwater Lecture Notes Flashcards

Flashcards covering the fundamental concepts of groundwater, including porosity, permeability, flow dynamics, extraction methods, and quality concerns.

Porosity

The percentage of open space within an unconsolidated sediment or a rock.

Primary Porosity

The spaces represented by the gaps between grains in a sediment or sedimentary rock.

Secondary Porosity

Porosity that develops after a rock has formed, such as fracture porosity or cavities within fossils.

Permeability

A description of how pore spaces are shaped and interconnected, determining how easily water can flow through the material.

Hydraulic Conductivity ($K$)

A measure of the permeability of a geological material, expressed in units of velocity such as $\text{metres per second}$.

Aquifer

A body of rock or unconsolidated sediment that has sufficient permeability to allow water to flow through it.

Aquitard

A body of geological material that does not allow the transmission of a significant amount of water, such as clay or till.

Unconfined Aquifer

An aquifer that is exposed at the ground surface.

Confined Aquifer

An aquifer separated from the ground surface by a lower permeability material known as a confining layer.

Confining Layer

The aquitard material that separates the ground surface from a confined aquifer.

Unsaturated Zone

The area above the water table where pore spaces are occupied by both water and air.

Saturated Zone

The area where all pore spaces are $100\%$ filled with water.

Water Table

The upper surface of the saturated zone.

Recharge Area

The region where water from precipitation flows downward through the unsaturated zone to reach the water table.

Discharge Area

The area toward which groundwater flows and eventually exits to the surface, such as a stream or lake.

Potentiometric Surface

A measure of the total potential energy of the water in a confined aquifer, representing the level to which water will rise in a well.

Artesian Well

A well drilled into a confined aquifer where the water rises above the top of the aquifer to the level of its potentiometric surface.

Flowing Artesian Well

An artesian well where the potentiometric surface is above ground level, causing water to flow out of the well without pumping.

Perched Aquifer

An aquifer that exists above a regular unconfined aquifer because of an aquitard of limited extent.

Darcy's Equation

An equation used to estimate the volume of groundwater flow: $Q = K \times i \times A$, where $Q$ is volume flow, $K$ is hydraulic conductivity, $i$ is hydraulic gradient, and $A$ is cross-sectional area.

Darcy Flux ($q$)

A description of how much volume of water passes through each unit area of an aquifer, calculated as $q = K \times i$.

Equipotential Lines

Lines within an aquifer that represent points of equal pressure (hydraulic head).

Karst

A type of landscape formed from the dissolution of soluble rocks like limestone, characterized by caves and underground drainage systems.

Spring

A location where the water table intersects the ground surface, allowing groundwater to flow naturally to the exterior.

Well Casing

A steel pipe used to line a well to prevent it from caving in, typically around $15\,\text{cm}$ for domestic use.

Well Screen

A device installed at the bottom of a well casing with holes sized to allow water in while preventing aquifer particles from entering.

Cone of Depression

The V-shaped depression in the water table or potentiometric surface surrounding a well where water is being withdrawn.

Observation Wells

Non-pumped wells used to monitor groundwater levels, chemistry, and quality over time.

Environmental Flow Needs

The amount of water required in surface streams to meet the needs of the ecosystem, such as supporting salmon populations.

Adsorb

The process by which ions dissolved in water become attached to the surfaces of minerals, such as clay.

Acid Rock Drainage (ARD)

Acidity generated when sulfide-bearing minerals like pyrite ($FeS_2$) are exposed to water, oxygen, and bacteria ($Acidithiobacillus\,ferrooxidans$).

Septic System

A self-contained underground wastewater treatment system consisting of a septic tank and a drainage field.

Leachate

Rainwater that flows through refuse in a landfill, picking up contaminants along the way.