groundwater aquifer / aquitard water table groundwater flow groundwater contamination
TRANSCRIPT
Groundwater
• aquifer / aquitard
• water table
• groundwater flow
• groundwater contamination
Groundwater: aquifers
• Any geologic unit through which water can move easily (i.e. it’s permeable)(= high permeability)
• Porosity: how much water a geologic material can hold
Opposite of an aquifer?
• Aquitard / aquiclude– retards the flow of groundwater (it’s
almost never really zero)
Groundwater: aquifers• What would be the properties
(porosity/permeability) of conglomerate?
• High porosity, high permeability
Groundwater: aquifers• What would be the properties
(porosity/permeability) of unfractured granite?
• Low porosity, low permeability
Groundwater: aquifers• Can you think of a rock/sediment
with high porosity and low permeability?
Groundwater: aquifers• Can you think of a rock/sediment
with low porosity and high permeability?
discharge=2000 ft3/s
discharge=4000 ft3/s
How is this possible?
No tributaries
here
Ground Water and Surface Water
• These are almost always connected• If a stream contributes water to the
aquifer it’s called a “losing stream”• If a stream receives water from the
aquifer it’s called a “gaining stream”• Same stream can be both at different
places or at different times
Pumping Animation
• Go to animation at: http://almandine.geol.wwu.edu/~dave/courses/2003/spring/101/lectures/water_level.swf
What is happening here?
• In the low permeability case the water is pumped primarily from the area directly around the well, whereas with the higher permeability the water seems to be drawn from a more broad area surrounding the well "hole". Since permeability refers to the ability of a material to let a fluid move through it, the low permeability doesn't allow the water to venture far from the path of pressure change (the "hole" of the well).
• What happens when this well is heavily pumped?
Groundwater Flow
• Groundwater velocity– Depends on permeability and hydraulic
gradient (slope of water table)– Ranges from 100 m/day to mm/day– A good round number: 1 ft/day
• What happens when a new well here is heavily pumped?
Flow direction
can change