Transcript Chapter 14 Groundwater - Seymour Community School District

Chapter 14-1 Groundwater
Pages 298-315
Geology
Groundwater
Factors that affect the amount of seepage of
water into the ground are:
1.Type of rock or soil on the ground where
the water falls
2.Climate, topography, land use, vegetation
Porosity
• The percent of a materials volume that is
pore space – the more the space, the more
water that can be held.
• Depends on:
– Particle shape
• More rounded particles allows for more pore spaces
– Sorting
• Well sorted material (same size) offers greatest pore
spaces
Permeability
• The rate at which water or other liquids pass
through the pore spaces of a rock.
– Permeability increases with grain size
– Ex: sand and gravel is highly permeable while
clay and shale has low permeability.
– So, can a rock be highly porous but not be
permeable? – explain…
– Or, can a nonporous rock become highly
permeable?
The water table
• The water table is the upper surface of the
zone of saturation
• Above this level up to the surface, the
ground can still hold more water, and this
area is called the zone of aeration
– This zone of aeration contains 3
parts:
• The three parts of the zone of aeration
are:
– 1) capillary fringe
• Found just above the water table,
where water rises due to water’s
attraction to the soil particles.
• This is called Capillary action
– 2) a dry region of soil except after
rainfall
– 3) organic or humus layer just below the
surface
What are some factors that affect the depth of the water table
How is the water table important?
• Seepage from water table keeps streams
flowing between rain events
• Maintains water levels of lakes and
wetlands
• Provides drinking water from natural springs
and human-made wells
Types of wells
• Ordinary well
– Water must be pumped out of the well
• Artesian well
– Well water is under some pressure to force the
water up the well – does not have to be to the top.
Large volumes of water found underground in the
pore spaces is called an aquifer.
***best aquifers are those made of uncemented
sands and gravel, followed by porous sandstones.
View of an artesian formation
How does a geyser occur?
• Geyser animation
Conserving Groundwater Water Budgets
Chapter 14-2
Pages 306-307
Water budget
• Describes the income and spending of water
for a region.
– The income is rain or snow
– The spending includes water loss by use, runoff,
and by evapotranspiration.
• Weather is the controlling factor of evapotranspiration
- when temperatures are high, the amount
of evapotranspiration would also
increase.
- the opposite is also true, low temperature
causes low evapotranspiration.
Four parts of a water budget
• Recharge
– When moisture is added to the groundwater, the soil
water storage is filling
• Surplus
– Occurs when the rainfall is greater than the need for
moisture, and the storage water is filled
• Usage
– If the need for moisture is greater than the rainfall and
the plants draw water from the soil water supply
• Deficit
– Occurs when the need for moisture is greater than the
rainfall and the soil water is gone.
Examples of water budget
Another water budget example
Water conservation
• In many regions, water is being used at a
faster rate than can be naturally
replenished.
Pollution is also threatening many
groundwater supplies
Percent water consumption
Overuse of groundwater
• When groundwater supplies are depleted,
the water table drops
– This may cause wells, springs to go dry
– If this happens along coastal regions,
salt water may seep into overused
freshwater aquifers and damage water
supplies by making them salty and
unusable.
• Overuse of groundwater
may cause ground levels to
drop due to compaction of
the removal of groundwater
below.
– Entire valleys may
subside like the San
Joaquin Valley of
California (up to 30 feet
drop from 1925-1977)!
Sinkholes may form
from loss of groundwater
• In Florida
• In Bowling Green, KY
Groundwater pollution
• Groundwater may become polluted by
human activities:
– Fertilizer
– Oil from roadways
– Pesticides
– Sewage from septic tanks and sewers
– Hazardous wastes from industry
– Toxic waste dumps (Love Canal – New
York)
Images of Love Canal
Groundwater and Geology
Chapter 14-3
Pages 309-311
Geologic formations formed by
groundwater
• Groundwater moving through bedrock may take in
dissolved minerals.
• This water is now called “hard water”.
Calcium ions is most common mineral in hard H2O
• What do we do at home to reduce hard water?
• Hard water causes water spots, poor washing
• Artesian water is usually harder than regular
groundwater
• Groundwater is almost always harder than river
water
Mineral deposits
• When water evaporates or cools, it will leave
behind any minerals that were dissolved in the
water.
– Examples: geyserite, geodes, mineral veins of
copper, quartz, gold, silver, calcite, etc.
• Petrified wood is formed when minerals replace
decaying wood of buried trees
• Calcite is most common dissolved mineral
cement for grains of sand and pebbles.
Mineral springs
• A spring with a high concentration of mineral
matter
– May be due to:
• Hot water
• Water passes through easily dissolved
minerals
• Water contains large quantity of gases
• Some mineral springs areas have become
health resorts – Hot Springs, Arkansas
• Yellowstone’s Mammoth Hot Springs forms
calcium deposits called traventine
Caverns
• Formed in areas with limestone bedrock
• Limestone is dissolved by carbonic acid found in
the groundwater
– Dripstone
– Stalactites
– Stalagmites
• When they meet, they form columns or
pillars
• Examples include Mammoth Cave in Kentucky,
caves of Calumet and Door County, WI, Eagle
Cave west of Madison
Karst Topography
• Identified by sinkholes, sinkhole ponds,
fissures, lost rivers, and underground
rivers
• Created when caverns collapse
• Forms where bedrock is made of calcite or
dolomite
• Found in south-central Kentucky, Door
County, WI