ELSS - Aquifers, artesian basins, springs, groundwater extraction & recharge Flashcards
Where does precipitation go into the ground?
Groundwater Store
What is an aquifer?
An area of porous rock saturated with groundwater
What are the two types of aquifers?
Confined and Unconfined
What can the confinement of water lead to?
Artesian pressure
How can water be extracted from an confined aquifer?
- Drill wells
- Pumps
- Boreholes
Why don’t you need pumps to yield water sometimes?
Sometimes the pressure is enough to force the water to the surface
What can lead to the lowering of the water table?
Rate of extraction > rate at which precipitation replenishes it
What happens if the water table is lowered?
- Springs dry up
- Artesian pressure drops
- Pumps need to be used to bring water to the surface
How can groundwater recharge happen?
- Infiltration and precipitation
- Irrigation/reservoirs
- Groundwater leakages from neighbouring aquifers
- Seepage through banks
What is a spring?
A water source formed when a land surface interacts with a flowing body of groundwater at or below the local water table
What else can an aquifer form in?
Pervious rock, e.g., limestone
How can aquifer form in limestone?
- Limestone fractures
- Carbonation occurs
- Water reaches a non-carbonate rock
- Stream flows horizontally
- Large cave formed
- Springs can emerge
What is surface water extraction?
Extraction, from ponds, rivers and lakes for industrial or agricultural use
What is the potentiometric surface?
The imaginary surface which the defines the theoretical level at which water could rise to in a confined aquifer
What is artesian pressure?
The hydro-static pressure exerted on groundwater in a confined aquifer, occupying an synclinal structure
