(TEST 2) Earth Science, Lecture pt 5 (ch 11) Flashcards
What is groundwater?
The water beneath the ground surface that is
stored within pores and fractures within the substrate
What is a major component of the hydrologic cycle?
Groundwater
What is a vital resource used for drinking water, agriculture, and industry?
Groundwater
Some precipitation enters the subsurface by
Infiltration
Infiltration water adds….?
Soil moisture and groundwater
Groundwater often resides in
Subsurface pore spaces
What are pores?
Open spaces within any sediment or rock
What is porosity?
The total volume of open space within sediment or rock
What is permeability?
The ease of water flow due to pore interconnectedness
What is hydraulic conductivity?
The ability of water to
move through a material
What is an aquifer?
A sediment or rock that can store and transmit water easily
What is an aquitard?
Impermeable or low permeability sediment or rock that hinders water flow
What are the two types of aquifers?
- Confined
- Unconfined
What is a confined aquifer?
An aquifer beneath an aquitard or an aquifer sandwiched between two impermeable layers
What is an unconfined aquifer?
An aquifer that intersects the surface
What type of aquifer is more likely to get polluted?
Unconfined aquitard
The water table is a subsurface
boundary where:
Pores are mostly filled with air above the water table and pores are filled with water below the water table
What is the unsaturated zone?
Where pores are filled with air above the water table
What is the saturated zone?
Where pores are filled with water below the water table
How does the water table position change with rainfall?
- During seasonally rainy periods, the water table rises
- During prolonged droughts, the water table falls
When do ponds/streams dry up?
When the water table falls below the bottom
What do lens-shaped aquitards prevent?
They prevent downward infiltration to the regional water table. Additionally, they lead to a perched water table
What is the potentiometric surface?
The elevation to which water in a confined aquifer would rise if a well were sunk into it
What do artesian wells do?
They tap into confined tilted aquifers. The water rises to the potentiometric surface without having to be pumped
Water distribution system mimics…..?
Artesian aquifers. Water is being pumped to an elevated storage tank
In an unsaturated zone, flow moves…
Straight downward
In a saturated zone, flow is….
Complicated because it’s governed by gravity and pressure
Groundwater flow rate is governed by several factors, what are they?
- Permeability of the porous material
- The effect of friction between water and conduit walls
- The spatial change in hydraulic head to hydraulic gradient
When do springs occur?
When groundwater discharges
at the surface
Springs can occur in
many forms, what are they?
- Discharge along the
side of a hill - Discharge from a
solution passageway in
limestone - Discharge along faults
or fractures in the rock
Deep springs tend to be
Saline
What is a hot spring
Groundwater discharges of hot water
Hot springs waters are usually high in
Dissolved minerals
What 2 settings do hot springs develop in?
- Where deep groundwater surfaces along faults
- In geothermal regions
What is the source of heat in hot springs?
The geothermal gradient
High geothermal gradients are linked to
Shallow magma
What is cone of depression?
An area lacking groundwater due to the rapid withdrawal by a well
What can drawdown cones do?
They can can pull contaminants into a well and reduce flow
to nearby streams or springs
What is the recharge zone?
An area where water infiltrates downward from surface to groundwater
What is the discharge zone?
Area where groundwater is removed from an aquifer, such as a spring, well, river, etc.
Groundwater mining is
Groundwater is being used at an unsustainable rate. Pumping rate is higher than the recharge rate
What does water in pore spaces hold apart?
Grains
Subsidence is mostly
Irreversible
Intense pumping in coastal communities can lead to
Saltwater intrusion
What happens to pore pressures as water is removed?
They decrease
What causes compaction in sediments?
Weight from overlying rocks
What is desalination?
The removal of mineral extracts from saline water
Distillation is also known as
Reverse osmosis
What are some alternative sources to freshwater?
- Reclaimed or recycled wastewater
- Aquifer storage and recovery
- Rainwater harvesting
- Conservation
- Xeriscaping
- Directed irrigation
- Drip irrigation
Where does most water contamination come from?
They come from the surface
What are some sources that contamination comes from?
- Septic systems
- industrial activities
- roads
- parking lots
- older sanitary landfills
- waste dumps
- agriculture
