Transcript of Groundwater -presents-. How large amounts of water are stored underground. How groundwater dissolves...
- Slide 1
- Groundwater -presents-
- Slide 2
- How large amounts of water are stored underground. How
groundwater dissolves limestone and forms caves and other natural
features. How groundwater is removed from the ground by humans and
what problems endanger our groundwater supply.
- Slide 3
- Infiltration Porosity Zone of saturation Water table
Permeability Impermeable Aquifer Topography Cave Stalactite
Stalagmite Travertine Spring Geyser Drawdown Artesian Well
- Slide 4
- The Hydrosphere The hydrosphere is water on or in Earths crust.
hydros is the Greek word for water. 97% Ocean Water 3%
freshwater
- Slide 5
- 97% Ocean Water From the 3% of freshwater, how much do you
think is trapped in the polar ice caps and glaciers? a. 10% b. 50%
c. 90%
- Slide 6
- ?? ?? ?? ?? What is the greatest source of freshwater on Earth?
a.Polar caps a.Glaciers a.Both a and b
- Slide 7
- Precipitation and Groundwater
- Slide 8
- Much of the precipitation that falls on land enters the ground
through a process called infiltration and becomes groundwater. Only
a small portion of runoff is directly returned to the oceans
through streams and rivers.
- Slide 9
- Precipitation and Groundwater Solid precipitation such as snow
takes a long while before it becomes runoff or infiltrates to
become groundwater. Eventually, the groundwater returns to the
surface through springs and then flows back to the ocean.
- Slide 10
- Groundwater Storage The amount of space between rock particles
in underlying sediment is referred to as porosity. Well sorted High
sediments Porosity
- Slide 11
- Groundwater Storage The amount of space between rock particles
in underlying sediment is referred to as porosity. Poorly sorted
Low sediments Porosity
- Slide 12
- Groundwater Storage Q: Which of these two do you think will
absorb groundwater faster after rainfall? a.b.
- Slide 13
- Groundwater Storage The porosity of sand can range from 2% to
50% ! The greater the porositythe faster water is absorbed.
- Slide 14
- The Zone of Saturation The depth below the Earths surface at
which groundwater completely fills the pores of material is called
the zone of saturation.
- Slide 15
- The Zone of Saturation The upper boundary of the zone of
saturation is called the water table.
- Slide 16
- The Zone of Saturation Only the water that exists in the Zone
of saturation is called groundwater.
- Slide 17
- The Zone of Saturation Zone of aeration materials are moist but
contain mostly air.
- Slide 18
- The Water Table The depth of the water table varies with the
slope of the land.
- Slide 19
- The Water Table The topography of the water table follows the
contours of the land.
- Slide 20
- The Water Table The water table rises and falls depending on
the season and the amount of precipitation.
- Slide 21
- ?? ?? ?? ?? Where is the water table closest to Earths surface?
a.Floodplain a.A Swamp a.A Hilltop
- Slide 22
- Groundwater Movement In saturated sediment all materials are
coated with a thin film of motionless water. In coarse grained
materials like sand, this film occupies a relatively small portion
of the pore space. 1 mm
- Slide 23
- Groundwater Movement Because of this moving water can flow
freely past the open pore spaces. Groundwater flows downhill due to
gravity and in the direction of the landscape slope. 1 mm
- Slide 24
- Groundwater Movement Because water has to squeeze through the
small pores in the subsurface material, it usually travels very
slow. 1 mm
- Slide 25
- Groundwater Movement Sometimes the pores are so small not even
a single water molecule can get through. 1 mm 0.1 mm vs.
- Slide 26
- Groundwater Movement The ability of a material to let water
pass through it is called permeability. 1 mm 0.1 mm vs.
- Slide 27
- Groundwater Movement Q: Which of the two examples of sediment
above have the highest permeability. 1 mm 0.1 mm vs. Highly
permeable materials include sandstone, limestone, and fractured
bedrock. Flow rates for these materials can be as fast as 1 m/h
(one meter per hour).
- Slide 28
- Groundwater Movement 0.1 mm With such tiny pores, some fine
grained material is considered impermeable. 0.1 mm Flow velocities
in impermeable materials are often measured in m/yr (meters per
year). Examples of impermeable materials are silt, clay, and
shale.
- Slide 29
- ?? ?? ?? ?? What two factors determine the flow velocity of
groundwater? Answer: The flow velocity depends on the slope of the
water table and the permeability of subsurface materials.
- Slide 30
- Groundwater Movement Most groundwater flow takes place through
permeable layers called aquifers.
- Slide 31
- Groundwater Movement Impermeable layers called aquacludes are
barriers to groundwater flow.
- Slide 32
- ?? ?? ?? ?? What is an aquifer? Answer: An aquifer is a
permeable layer that allows groundwater to flow through it.
- Slide 33
- Springs Aquifers are commonly composed of sand, gravel,
sandstone and limestone. Remember: Limestone is easily dissolved by
groundwater..thats how cavities in aquifers appear. (A cavity is an
open spacelike a cave).
- Slide 34
- Caves Caves form near or below the water table.
- Slide 35
- Caves Stream valleys are lowered and streams become empty as
they infiltrate cave openings.
- Slide 36
- Caves Collapsing caves (or dissolved bedrock) near the surface
of the Earth produce sink holes on the Earths surface.
- Slide 37
- ?? ?? ?? ?? Since the Limestone area of an aquifer is filled
with cavities, how would this affect the rate of groundwater flow?
Answer: Since there are a lot of open spaces due to dissolved
limestone, the ground water can flow FASTER in this area of an
aquifer.
- Slide 38
- Caves Caves are usually located just beneath the water table.
As water drips from the ceiling of a cave, it leaves behind small
trace amounts of minerals found within the water itself. After a
long period of time, these minerals collect to form cone shaped
structures called stalactites.
- Slide 39
- Caves As the water drips to the floor, minerals left begin to
build up mound shaped, dripstone deposits. This type of deposit is
called a stalagmite. Eventually, stalactites and stalagmites will
join together to form dripstone columns within the cave!
- Slide 40
- ?? ?? ?? ?? So what happens when an aquifer meets an aquaclude?
Answer: The aquaclude stops water flowso when aquifers and
aqucludes meet, water is forced out of the Earth.see photo on page
249.
- Slide 41
- Springs When aquifers meet aquacludes at or near the surface of
the Earth, water is forced out of the Earth.thus producing a
SPRING.
- Slide 42
- Springs The volume of water produced by a spring can be a mere
trickle or a raging river! In a Karst Region, springs yield
extremely fast moving waters.. theyre called Super Springs.
- Slide 43
- Springs In areas where there is horizontal sedimentary rock,
Springs emerge in valleys very close to aquifers.
- Slide 44
- Springs Springs can occur at the edges of perched water
tables.
- Slide 45
- Springs Sometimes Springs emerge along fault lines! Springs can
also emerge at fault lines.
- Slide 46
- Springs Sometimes Springs emerge along fault lines! In
Limestone regions, springs discharge water from underground
pathways.
- Slide 47
- Winter Summer Temperature Of Springs Spring water can be hot,
warm, or cold.depending upon where the spring is located. Air Water
Air Water
- Slide 48
- Temperature Of Springs
- Slide 49
- Temperature Of Springs Hot Springs are defined as groundwater
with temperatures higher than that of the human body.
- Slide 50
- ?? ?? ?? ?? So where do hot springs get their heat from ?
Answer: Hot Springs get their heat from aquifers deep within the
Earth.
- Slide 51
- Temperature Of Springs Sometimes the groundwater from these
aquifers absorb so much heat..they erupt! Hot Springs that erupt
are called geysers!
- Slide 52
- Wells The red dashed line represents where the water table used
to be before most of the water was pumped out!
- Slide 53
- Wells The distance between the deepest part of the cone of
depression and the old Water table line is called drawdown.
- Slide 54
- Wells Eventually, water from runoff and precipitation is added
back to the zone of saturation. This process is called
recharge.
- Slide 55
- Confined Aquifers Water-table aquifers are often polluted when
chemicals spill on surface sediment.
- Slide 56
- Confined Aquifers If an aquifer is located between two
aquacludes, it can be protected from pollution.
- Slide 57
- Confined Aquifers In essence, the aquacludes become body guards
to the aquifer.
- Slide 58
- Confined Aquifers An aquifer sandwiched between two aquacludes
is referred to as a Confined Aquifer.
- Slide 59
- Confined Aquifers Confined aquifers usually contain water under
pressure since the area of recharge is at a higher elevation.
- Slide 60
- Confined Aquifers Confined aquifers usually contain water under
pressure since the area of recharge is at a higher elevation.
- Slide 61
- Confined Aquifers This type of aquifer is called an Artesian
aquifer and water that spurts from it is called an Artesian
Well.
- Slide 62
- Slide 63
- Pollutants from sewage travel downslope to contaminate
wells.
- Slide 64
- Protecting Our Water Supply There are a number of ways in which
groundwater resources can be protected and restored. All major
pollution sources need to be identified and eliminated.