Geology Chapter 11
confined aquifer
An aquifer that is overlain by an aquitard such that it is sealed off from the atmosphere and surface environment, creating pressurized conditions with the aquifer. Also called an artesian aquifer.
What does consumptive water result from?
Human activities where water is lost and cannot be used again.
consumptive water use
Refers to those human activities where water is removed from its source and is lost or consumed.
What makes human life possible and our planet so unique within the solar system?
The Earth's abundance of liquid water
What is off-stream usage?
Where water is removed from a source, but discharged elsewhere after being used.
cone of depression
a cone-shaped depression in the water table or potentio-metric surface of an aquifer, which forms when the water level (hydraulic head) within a well is lowered by pumping.
aquitards
a geological material (rock or sediment) with low permeability that inhibits the flow of groundwater. Also acts as confining layers for artesian (confined) aquifer systems.
hydraulic head
a measure of potential energy within an aquifer system, and is represented by the height of the water table or potentiometric surface.
hydraulic conductivity
a measure of the ability of a material to transmit a fluid and is dependent on both the property of the material (permeability) and properties of the fluid itself (density and viscosity).
What is the hydraulic head?
a measure of water's potential energy within an aquifer and is related to the elevation of the water table or potentionometric surface
aquifer
a permeable geological material (rock or sediment) that readily transmits water. Often used as a supply source for groundwater.
spring
a place where groundwater discharges into the surface environment in a concentrated manner.
leakage
a term used to describe the process where groundwater moves between two different aquifers flowing across an aquitard.
unconfined aquifer
a type of aquifer that is open to the surface environment and includes a water table that marks the boundary between the saturated and unsaturated zones.
xeriscaping
a water conservation technique in which landscaping is done with native plants that require little to no irrigation water.
aquifer storage and recovery
a water management technique that involves storing surplus surface water in an aquifer, which is then removed at a later time when surface water supplies are more limited. Sometimes referred to as water banking.
Where do humans tap into the the freshwater?
as it moves through the surface and subsurface portions of the hydrologic cycle.
Why are clay-rich materials and unfractured crystalline rocks called aquifers?
because they do not transmit much water.
How is the water level in an unconfined aquifer defined?
by the water table
How do conservative techniques make more water available?
by using existing supplies more efficiently.
What are alternative means of increasing existing water supplies?
desalinization and reclaimed waste water.
Where does the fresh water from the hydrologic cycle go?
falls on landmasses where it flows into rivers and lake and infiltrates the subsurface.
Why are dams valuable?
for stockpiling water.
What are other sources of aquifers?
fractured rocks and solution limestone.
groundwater
fresh or saline water that resides within the void or pore space of subsurface materials.
What are the most desirable aquifers?
granular materials like gravel and sands because they can transmit larger volumes of water.
freshwater
low salinity water that originates as precipitation within the hydrologic cycle.
water table
marks the boundary between the unsaturated and saturated zones, below which all the pore spaces are filled with water.
What are aquifers?
materials that easily transmit water.
off-stream use
refers to those human activities where water is removed from on supply source, but then returned to a different source after being used.
potentiometric surface
represents the height that water in a well will rise above a confined aquifer, and is a measure of the amount of potential energy within the aquifer
hydrologic cycle
the cycle movement of water within the Earth system , driven by solar radiation that causes water to evaporate from the oceans and land surface.
Examples of consumptive water use
the irrigation of crops and production of concrete
desalinization
the process of removing the dissolved ions from saline water, by either distillation or reserve osmosis, in order to generate freshwater that is suitable for human consumption.
saltwater intrusion
the undesirable situation where the human withdrawal of groundwater allows saline water to migrate into the freshwater portion of an aquifer that is being used as a water supply.
groundwater mining
the undesirable situation where the human withdrawal of groundwater is greater than the rate of natural recharge, causing water levels in an aquifer to get progressively lower over time.
example of off-stream use
the withdrawal of groundwater that is later discharged into a stream
How can dams be harmful?
they can discharge cooler water and trap sediment, which can damage downstream ecosystems and fisheries.
How does the hydrologic cycle create fresh water?
through evaporation
Where does groundwater flow?
toward areas of hydraulic head
