Lesson 14: Ground Water Flashcards
What is the main use of groundwater in the U.S.?
Irrigation (Agriculture)
Where does the groundwater stay in the rock?
in open spaces (pores) within rocks and unconsolidated sediments.
What is porosity?
The percentage of open pore space within an unconsolidated sediment/rock
What is permeability?
How connected the pore spaces are to one another; controlled solely by pore geometry
Compare porosity and permeability
Porosity: determines how much groundwater can be stored
Permeability: determines how well water can flow from one pore to another
Define vadose zone.
The unsaturated zone above the zone of saturation; includes both air and water
Define saturated zone.
The zone of saturation where all pore spaces are completely filled with water; water in this zone is groundwater
Define water table.
The upper limit of the zone of saturation.
Compare losing and gaining streams.
Losing Streams: streams lose water to the groundwater system by outflow through the streambed; the water table is lower than the level of a stream
Gaining Streams: streams gain water from the inflow of groundwater through the streambed; the water table is higher than the level of the stream.
What is an Aquitard?
an impermeable layer that hinders/prevents groundwater movement
What is an Aquifer?
A porous and permeable zone that is saturated with water that is recharged as surface water seeps downward
What types of rocks make an aquitard?
Shale/mudrock and clay
What types of rock make an Aquifer?
Sand and glacial till
What is a confined aquifer?
An aquifer that has permeable rock units enclosed within impermeable rock units; recharged in highlands where permeable rocks are exposed
What is an unconfined aquifer?
An aquifer that is connected to the surface by open pore spaces through which it can be recharged
What is a perched aquifer?
When there is a limited aquitard; it may be a good source of water during some parts of the year, but is very thin and small, and can be depleted easily.
What is drawdown?
As water is withdrawn from a well, the surrounding water table is lowered.
Where do drawdowns form?
at the water table