Lecture 14: Groundwater Flashcards
What is Groundwater?
Water below the earth’s surface that fills voids in soils and rocks
How much of the earth’s water is groundwater?
Less than 1%
What is Recharge?
When water enters into the subsurface and becomes groundwater by percolating into soil or rock at the surface
Why is groundwater a critical resource for municipal water supplies?
Because there is approximately 35 times more groundwater than surface water
What are the two zones of the Groundwater?
Vadose zone and the Saturated zone
What is the Vadosone?
The region of groundwater nearer to the surface where pores or fractures in the subsurface are not entirely filled with water
What is the Saturated zone?
Where an aquifer beginfs
What is the water table?
The surface where the vadose zone meets the saturated zone in the water table
What is Porosity?
The amount of pore space in a geologic medium (soil, sediment, or rock) normally given between 0 to 1, or 0% to 100%
What is Permeability?
A measure of the ease with which a fluid (water in this case) can flow through a geologic medium
What is the meaning of the water is a often a subdued imitation of the landscape?
It means that it rises under hills and becomes lower in valleys
How does the water table vary with the season?
During times of low precipitation, the water table lowers and during times of recharge the water table rises
In what direction does Groundwater flow?
From regions of higher pressure to regions of lower pressure, driven by gravity
What are usually surface expressions of groundwater?
Rivers, lakes, ponds and wetlands
What is the Hydraulic Head?
The measure of pressure difference that drives groundwater flow
Where does Groundwater flow to and from?
Groundwater flows from recharge areas to discharge areas
What is a region of discharge?
One at which groundwater emerges at the surface
What are common discharge areas?
Surface water bodies rivers, lakes, streams, wetlands) and springs
What are Springs?
Natural points of groundwater discharge that occur when the water table of a permeability boundary intersects the land surface
What are Aquifers?
Units of geologic media that have sufficient capacity and high enough permeability to supply water at a rate useful to humans
What are the two types of Auifers?
Unconfined aquifers and confined aquifers
What are Unconfined Aquifers?
One in which the upper boundary is defined by the water table
What is a confined aquifer?
One in which the upper boundary is defined by an aquiclude
What are Aquicludes?
Units of geologic media that considerably stop the flow of water
