Download Spring, 2016 Mrs. Kummer - Van Buren Public Schools

Spring, 2016 Mrs. Kummer
Groundwater: Water that seeps down from
the surface of Earth
It is NOT runoff or part of a river
It fills all the air-filled openings/pores
between rock particles
90% of Earth’s fresh water is stored
beneath the surface
In the USA, groundwater supplies 1/5 of
our freshwater supply
Aquifer: A large body of rock in which large
amounts of groundwater can flow and also be
stored
Some aquifers are more efficient than others
Efficient ones are made of sandstone (large
pore spaces) or limestone (sharp fractured rock)
If the pore spaces or fractures are not
connected, then groundwater cannot flow easily,
making it an inefficient aquifer
The largest aquifer in the USA
is the Ogallala
Aquifer, under the Great Plains from TX to ND
Porosity: The amount of water a rock can hold
 It is usually stated as a percentage of open spaces in a
given volume of rock
Open Spaces can be:
Fractures
Cavities caused by erosion
Pores between rock particles
High Porosity = Efficient Aquifer
Sorting a HUGE factor in Porosity
Sorting: Natural amount of similar sized particles
Well sorted large grain rocks = HIGH porosity
Well sorted small grained rocks = HIGH porosity
Poorly sorted rocks = LOW porosity
Permeability: How freely groundwater can pass
through open spaces of a rock
To be permeable, the open spaces MUST BE
connected
A rock can have high Porosity but if open spaces
are not connected, NOT PERMEABLE
Larger, more consistently sorted particles = MORE
PERMEABLE
Sandstone and Limestone are HIGHLY PERMEABLE
Clay has fine particles packed tightly together
Clay =LOW PERMEABILITY or we say IMPERMEABLE
How Groundwater Happens:
Gravity pulls H2O down through rock until it reaches
impermeable rock→ H2O fills the pores above
impermeable layer → this H2O water level rises
underground → creates the zone of saturation
The top of the zone of saturation = the water table
Florida’s Water Table is very high/near surface, so
no basements allowed
Belleville’s water Table is also high, so many areas
with no basements
The zone that lies between water table and the earth’s
surface = zone of aeration
The zone of Aeration has 3 regions:
1. Top Region = Soil H2O, thin film around Top Soil
2. Bottom Region (just above water table) =
capillary fringe
Water is drawn up this layer like a Bounty
quicker picker upper paper towel. H2O is
attracted to other things like soil/dryness
3. Middle Region = a dry section most of the time.
Should only be wet during rainfall. If it is wet too
long, Capillary Fringe section stops its capillary
action…very bad
Zone of Aeration
Pros:
Useful for drinking and irrigation
Available year-round
Exists almost everywhere
Renewable if not overpumped or
contaminated
No evaporation losses
Cheaper to extract than most
surface waters
Cons:
Aquifer depletion from overpumping
Sinking of Land from overpumping
Aquifers polluted for decades or centuries
Saltwater intrusion into drinking water
supplies near coastal areas
Reduced water flows into surface waters
Increased cost and contamination from
deeper wells
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Two ways groundwater comes to the surface:
Wells and
Springs
Well: a hole dug below the water table and fills with
groundwater
Two Types of Wells:
Ordinary and Artesian
Ordinary Well: The well must go through highly permeable
rock below water table
If it isn’t permeable enough, water can’t flow into the
well as fast as it is being used
Cone of Depression: pumping water out of the well creates a
dip in the water table where there is no water
Pumping too much water continuously grows this region,
causing a well to go dry faster than it should
Springs: Natural flow of groundwater to the
surface that is found where the ground dips below
water table
Common is rugged terrains
Not continuous flow of water, depends on how
dry climate gets….more drought, less flow, spring
dries up
Perched water table:
a second zone of
saturation forms due to an additional layer of
permeable rock above a water table
Springs form where perched water tables meet
the surface are considered “permanent” springs
with continuous flow
Artesian Wells: Wells that are very far away from homes
(many cities away) with no pumps, and water flows freely
Artesian Formation: a special arrangement of permeable
and impermeable rock found in nature
Needs sloping layer near surface of earth made of
permeable rock sandwiched between two layers of
impermeable rock
The permeable rock = aquifer
Top layer of impermeable rock = cap rock
Water becomes pressurized by the weight of the pooling
water flowing downward
Artesian wells are dug into the aquifer just under cap rock
* When we deplete groundwater too fast it
creates air pockets underground
* We can also create fast soil erosion with
broken water pipes underground…
* Can the weight of houses, trucks, cars,
humans, etc. be supported by air??????
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Artesian/Fissure Springs: groundwater flows to surface from a
crack/fracture in cap rock….pressure from water in the aquifer
below pushes water through the crack
Hot Springs: Groundwater passing by regions with active
volcanic activity to heat the water before it comes to the
surface, with at least 37°C water
Mud Pots: Hot springs chemically reacting with volcanic gasses
and rocks on surface (sulfur, NOx, etc.) to make a sticky, liquid
clay..very toxic
Geysers: Hot springs erupting periodically at surface due to a
vent hole that has direct connection to a superheated water
vapor near heated rock/molten rock