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?

How is this possible? discharge=2000 ft3/s 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