High permeability: gravels, sands, limestones with dissolution channels, fractured rocks

Low permeability: clays, unfractured meta. and igneous rocks, limestones without dissolution
Aquicludes: rocks/seds that slow down groundwater movement

Zone of aeration: air and water in pore spaces
Zone of saturation: water fills pore spaces.

Water table: upper limit of zone of saturation

Water table has similar shape to ground surface, but varies with rainfall.

Groundwater moves from areas with high water table to low water table.
Velocity depends on the water table gradient and aquifer permeability.
 

Artesian (confined) aquifer: confined by aquicludes so pressure builds up.
Water in wells will rise above the top of the aquifer.

Perched water table: saturated area which is separated from the main water table.

Springs (where water flows onto ground surface)

Pumping from wells: cone of depression forms in water table

If pumping > recharge:

• water table drops: nearby wells can go dry.
• Subsidence: when water is removed, sediment compacts, lowering ground surface.
• Saltwater intrusion (incursion)

• limit pumping
• recharge water (treated waste water, excess runoff)
• physical barriers (for saltwater intrusion)