Hydrogeology Fundamentals

Comprehensive vocabulary flashcards covering the biological, physical, and chemical principles of hydrogeology, including the water cycle, aquifer properties, and groundwater flow mechanics from the lecture notes.

Hydrology

The study of water that addresses the occurrence, distribution, movement, and chemistry of all waters on Earth.

Hydrogeology

A descriptive and analytical science that encompasses the interrelationships of geologic materials and processes with water.

Hydraulics

The study of the movement of surface water.

Late Heavy Bombardment Hypothesis

A hypothesis stating that Earth's water was primarily extraterrestrial, delivered by water-rich asteroids and comets during a period of increased impact events approximately $3.8$ to $4.1$ billion years ago.

Outgassing

The release of trapped gas or vapor (such as $H_2O$, $CO_2$, and $SO_2$) that was previously dissolved, trapped, or frozen in the Earth's interior, often associated with volcanic activity.

Evapotranspiration

The combined process by which water moves from the land surface into the atmosphere, consisting of evaporation and transpiration.

Infiltration

The movement of water into rocks or soil through cracks and pore spaces.

Meteoric Water

Water that circulates in the atmosphere and co-exists with near-surface, uncemented sediments and subsurface rocks.

Connate Water

Water that forms in young marine sediments.

Juvenile Water

Water that has never circulated in the atmosphere.

Isolated System

A system that does not allow the transfer of either mass or energy.

Latent Heat

The energy associated with the physical state of water as it changes form between solid, liquid, and vapor.

Exothermic Process

A process that gives off heat, where the total energy of the products is less than the total energy of the reactants.

Endothermic Process

A process where heat must be supplied to the system, and the total energy of the reactants is less than the total energy of the products.

Heat Capacity ($C$)

A measurable physical quantity characterizing the amount of heat required to change a substance's temperature by a given amount, measured in $J/^\text{o}C$.

Specific Heat ($s$)

Also known as Specific Heat Capacity, it is the heat capacity per unit mass of a material, measured in J/g\text{\textperiodcentered}^\text{o}C.

Hydrologic Equation

A quantitative statement of the Law of Mass Conservation: $\text{Inflow} = \text{Outflow} \text{ ± } \text{Changes in storage}$.

Phreatophytes

Plants with a taproot system that extends deep enough to reach the water table.

Xerophytes

Desert plants with shallow root systems that spread out away from the plant to capture moisture.

Lysimeter

A device, typically a tank or container, used to directly measure evapotranspiration by defining a boundary for soil water and percolation.

Thiessen Method

A method for determining mean areal precipitation by creating polygons around stations to weigh their individual contributions separately.

Overland Flow

Runoff that occurs when the precipitation rate exceeds the infiltration capacity of the soil.

Baseflow

The portion of streamflow that is composed entirely of groundwater contributions.

Aquifer

A saturated, highly permeable geologic formation that both stores and yields water in adequate quantities.

Aquitard

A semipervious geological formation that transmits water at much slower rates than an aquifer.

Aquiclude

A saturated geological formation that can store water but cannot transmit it fast enough to yield a significant supply to a well.

Vadose Zone

Also called the Zone of Aeration or Unsaturated Zone, it refers to the portion of the subsurface located right above the water table.

Capillary Fringe

A narrow zone of saturation above the water table where water is pulled upward into pore spaces by capillary forces.

Porosity ($n$)

The capacity of a rock mass to accommodate fluid, defined as the percent volume of pore spaces to the total volume of the material.

Void Ratio ($e$)

The ratio of the volume of voids in a soil to the volume of the solid material.

Specific Yield ($S_y$)

The amount of water that can be extracted from an unconfined aquifer under the force of gravity.

Specific Retention ($S_r$)

The amount of water a soil or rock holds against gravity due to surface tension and molecular attraction.

Hydraulic Conductivity ($K$)

The ability of an aquifer to transmit fluid through interconnected pore spaces, depending on the properties of the medium and the fluid.

Intrinsic Permeability ($K_i$)

A property of a porous medium that is a function of the size and arrangement of the pore spaces, measured in units called Darcy.

Transmissivity ($T$)

The rate at which water is transmitted through a unit width of an aquifer under a unit hydraulic gradient, calculated as the product of thickness ($m$) and hydraulic conductivity ($K$).

Storativity ($S$)

Also known as the storage coefficient, it is the volume of water an aquifer releases from storage per unit surface area per unit decline in hydraulic head.

Bernoulli's Equation

An equation used to describe the total mechanical energy of a fluid, stating that the sum of velocity, elevation, and pressure heads is constant in a steady, frictionless flow: $E_T = \frac{v^2}{2g} + z + \frac{P}{\rho g}$.

Total Stress ($σ_T$)

The downward stress in an aquifer caused by the weight of the overlying rock and water.