Glossary#
A list of terms used in the QES course.
- Aquiclude#
Sometime refered to as an aquifuge; a rock with very low hydraulic conductivity that acts as an impermeable barrier to groundwater flow.
- Aquifer#
A body of permerable rock that is capable of storing significant quantities of water, underlain by impermeable material.
- Aquitard#
A rock with low values of hydraulic conductivity, but that still allows some flow of groundwater through it.
- Artisan Well#
A well that flows without pumping because the hydraulic head in the confined aquifer that feeds it is greater than that at ground level.
- Confined Aquifer#
An aquifer that is sealed by impermeable rock above and below.
- DIC#
Dissolved Inorganic Carbon - the sum of \(CO_2\), \(H_2CO_3\), \(HCO_3^-\) and \(CO_3^{2-}\) in water.
- Discharge#
The amount of water flowing at a particular point.
- Elevation Head#
The height in m above the reference datum, which is usually mean sea level in groundwater systems.
- Hydraulic Conductivity#
A combination of the physical properties of a fluid and the permeability of the medium it is flowing through which descibes how quickly the fluid can move through it, termed \(K\). This is a key property of hydrogeologic systems which is highly variable (12 orders of magnitude!) depending on rock type.
- Hydraulic Gradient#
The difference in hydraulic head per unit distance, \(\dv{h}{l}\)
- Hydraulic Head#
A measure of liquid pressure at a particular place (depth) relative to some datum (usually mean sea level). Descibes the amount of energy available in the system. Can be subdivided into the pressure head and elevation head (also kinetic head, although this is negligible in groundwater systems).
- Infiltration#
The downward entry of water into soil.
- Ocean Acidification#
A reduction in ocean pH caused by the dissolution of \(\mathrm{CO_2}\) into water.
- Percolation#
The downward movement of water through soil.
- Permeability#
The physical characteristics of a porous medium that allow water to flow through it. Related to porosity, but not identical - a porous rock is not necessarily permeable.
- Porosity#
The total sum of all void spaces in a rock. Often expressed as a percentage, or a number between 1 and 0. Not all these spaces may be connected, however, so for water flow, the effective porosity is the amount of void space that can hold and transmit water.
- Pressure Head#
The total absolute pressure exerted on a point in the system, expressed in m.
- Recharge#
The downward movement of water from the soil to the water table.
- Residence Time#
The average time that a given substance remains in a reservoir.
- Total Alkalinity#
A conservative quantity that can be used to track the equilibrium state of weak acids in water. Calculated as the sum of the negative ions of weak acids, minus \(\mathrm{[H^+]}\), this does not change as acid-base equilibria shift with temperature because it includes both the acid and base component of the system.
- Reynolds Number#
The ratio of inertial forces to viscous forces within a fluid. Fluids with a large Reynolds Numberare dominated by intertial forces, and fluids with a small Reynolds Number are dominated by viscous drag.
- Transmissivity#
The ability of an aquifer to transmit groundwater throughout its entire saturated thickness.
- Solubility Pump#
The movement of carbon around the ocean by physical-chemical processes. Surface water cools as it travels to higher latitude, allowing it to store more C and DIC. This downwells into the deep ocean, where it remains until that water is upwelled. The warming of upwelling water releases the stored C back into the atmosphere.
- Specific Discharge#
The flow rate through a system divided by its cross sectional area, \(q\).
- Storativity#
The volume of water released from storage per unit decline in hydraulic head in the aquifer, per unit area of the aquifer
- Unconfined Aquifer#
An aquifer where the water table defines the upper water limit.
- Water Footprint#
The total amount of water it takes to manufacture something.
- Water Table#
The upper surface of groundwater, or the level below which an aquifer is permamently saturated with water.