Water Supply and Waste Disposal Flashcards
Define Water Table
The upper limit of the saturated zone
Define Aquifer
A unit of permeable rock that can yield significant amount of water e.g. sandstone or limestone
Define Aquiclude
A unit of low permeability that controls water flow from aquifers e.g. shale or mudstone
Define Aquifuge (Aquitard)
An impermeable rock, no water is absorbed or transmitted e.g. granite
Define Recharge Area
Water gets into the aquifer from an area where the permeable rock is unconfined
Define Spring
Where water flows from an aquifer to the earths surface, where the water table meets the surface
Define Perched Aquifer
Occurs above the main water table in the saturated zone, when there is an impermeable layer of rock or sediment above the main water table/aquifer but below the surface of the land
Define Unconfined Aquifer
Water will seep directly into an underlying unit of permeable rock near the surface
Define Confined Aquifer
Water can’t seep directly into the unit of permeable rock because it is bound by two layers of impermeable rock
Define Darcy’s Law
A way of calculating the permeability of a rock or sediment
What are three things Darcy’s Law allows an estimation of?
The flow rate within an aquifer, The average time of travel from the area of recharge to a point located in the hydraulic gradient, Prediction of pollution plume arrival times
Define Hydraulic Gradient
The difference between hydrostatic pressure at two heights
What are four problems associated with over extraction of groundwater?
Cone of depression, Subsidence, Saltwater incursion, Soggy cellar syndrome
Define Cone of Depression
Forms when the extraction rate is greater than the rate of recharge, causing the water table to become drawn down in the immediate vicinity
Define Subsidence
When groundwater extraction exceeds the recharge rate of an area there is potential for the unconsolidated sediment to subside and ground levels to drop
