Transcript Water Unit

Water Unit
Aquifers
• Porous, water bearing layers of sand,
gravel and/or rock below earth’s surface
• Reservoirs for groundwater
• Latin: Aqua = Water
Ferre = To bring
2 Types of Aquifers
CONFINED
• Water is in porous,
fractured rock
• Can be artesian
(under pressure)
• Water is sandwiched
between two
impermeable layers
UNCONFINED
• Water is in
sandy/gravelly soil
• Impermeable layer
(ex: solid rock) is
beneath the water,
but not above
• Most common type
2 factors determine productivity:
1. Porosity – The amount of water it can hold
2. Permeability – The ability of water to flow
through it
Ogallala!
• Largest aquifer on earth
• Beneath 8 states, extending from N.
Dakota to Texas
• Once held more water than all of the
freshwater lakes, rivers and streams on
earth combined
• Excessive pumping has left no water in
some peripheral places
Groundwater Depletion
• Aquifer recharge can take
thousands of years
Depletion Examples:
• Cone of Depression
• Saltwater Intrusion
• Subsidence / Sinkholes
Cone of Depression and Saltwater Intrusion
Subsidence
Sinkholes
Surface
craters
caused by
collapse of
an
underground
channel
Rivers
Riparian Zone – The river and its stream banks
Watershed
• All the land drained
by a river
• The area retains
rainwater and lessens
downstream flooding
when vegetated
• Case Study:
Unregulated timber
cutting along Yangtze
caused 30,000 deaths
due to flooding
How to Improve Watershed Management:
•Less development
along floodplains
•Retain “crop
residue” on fields
•Minimize plowing
and forest cutting
on slopes
•“Buffer zones” of
vegetation near
waterways
Earth’s Largest Rivers
• Discharge rate – the amount of water that
passes a fixed point over a given amount of
time.
Amazon – Brazil, Peru
(175,000 m3/sec)
Orinoco – Venezuela
(45,300 m3/sec)
Yangtze – Tibet, China
(28,000 m3/sec)
Mississippi – US
(18,400 m3/sec)
Case Study: 3 Gorges Dam
• Largest dam in the world
• 1.2 million people relocated
• Fragile ecosystems and rare species
indigenous to that area were flooded
• Reservoir flooded thousands of villages
• Triggering landslides
• Dam is constructed above a fault line
3 Gorges Dam
Lake Stratification (draw it.)
Point Source Pollution:
•When a pollutant is
identified as coming
from a specific source
Plume – contaminants
that seep from a
concentrated mass.
•Ex’s: smoke from a
chimney, image to
the right 
Non-Point Source
Pollution
•Pollution that
does not have a
specific point of
origin
•Ex: parking
lots, residential
lawns
POLLUTION
Point-Source
Examples:
–Leaky
landfill
–Leaky septic
system
–Thermal
pollution
Non-Point Source
Examples:
–Runoff/erosion
from farms
–Parking lots
–Feedlots
–Atmospheric
deposition
Atmospheric Deposition
• Contaminants get into air
and are redeposited via rain
• Normal rain: pH ~ 5.6
• Acid Rain: pH <5
• Acid Precipitation leaches
out naturally occurring Al, Hg
• Has left 600,000 kg of
Atrazine (an herbicide) in the
great lakes
Pollution Consequences
• pH – acidity can be caused by industry
waste, acid rain, mine tailings (esp. coal
due to high S content)
• N,P,K – concentrations elevate upon influx
of fertilizer, manure…
• Oxygen level – measured in ppm. Air gets
into water via Ps (photosynthesis) and
wave action.
–O2 and BOD have an inverse relationship
(Polltn Consq. cont.)
Thermal Pollution:
•Heat in water
•Hot water can
hold less O2 than
cold water
•Sources:
•Power plants
•Industrial
coolant
•Your gutters
(Polltn Consq.)
Turbidity
(a.k.a. cloudiness)
• Increases due to
presence of sediment and
runoff, which use up
O2 during decomposition
•Turbidity itself isn’t necessarily bad. However, it is
often present in connection with pathogenic
organisms or an excess of decomposing material.
•Particles can bond with toxic substances,
transporting them and complicating removal
(Polltn Consq)
Infectious Agents
• Viruses, Bacteria
• Source: us and the animals
• Ex: Coliform
–Multiple types of coliform, all originate in
intestines
–Fecal Coliform – not necessarily
pathogenic, but in high levels is associated
with other pathogenic bacteria
Oxygen Demanding Waste
Oxygen Sag Curve
• Organic waste uses up
O2 in water during
decomposition
• 6-10ppm is considered
healthy O2 level
• Example organic
wastes:
– Leaves
– Food from
processing plants
– Sewage
Draw Oxygen Sag Curve
Cultural Eutrophication  Dead Zone
• Increased nutrition that enters a water
body, ultimately resulting in a lowered
oxygen level.
1. Increased nutrients enter a water body.
2. Causes an unsustainable algal bloom and
overgrowth of phytoplankton
3. Algae and phytoplankton use up
available oxygen when they decompose.
4. Fish suffocate.
Eutrophication cont.
• Can be due to:
–Increased nutrients, esp. N and P
• Ex: agricultural manure, fertilizer
–Elevated temperature
• Ex: Thermal pollution/increased
sunlight (which triggers unsustainable
algae growth, begins cycle…)
Gulf of Mexico “Dead Zone”
Eutrophication
Natural
Cultural
Blue Baby Syndrome
• Caused by excess nitrates in water
• Nitrates bind to red blood cells…especially
harmful to infants
• Causes baby to appear bluish due to lack
of O2 reaching cells (suffocation)
• Can cause death
• Many of Iowa’s “cornbelt” wells are nitrate
contaminated
Toxic Tide/Red Tide
(polltn cont.)
• Caused by dinoflaggelates –
unicellular, photosynthetic
microorganisms
• Population bulge can be due to natural
causes or due to excess nutrients in
waterbody
• Ex: pfiesteria piscicida – poisonous to eat
or breathe (causes memory loss, confusion,
acute skin burning, lesions…)
Radioactive Materials
(polltn. Cont.)
Sources: mining,
ore processing,
power plants, or
can be naturally
occurring
Ex: Cs, Th, U
Inorganic Chemicals
(polltn. cont.)
• Ex: Hg, Sn, Pb, Cd, Ni, As, Se
• Are often bioaccumulators (increase in
concentration as you move up the food chain)
• ppm levels can be fatal to humans
• Sources: household cleaners, industrial
effluent
• Ex: panning for gold in Amazon River. (use Hg
to bind to Au, then burn off Hg using torch)
Organic Chemicals
(polltn. cont.)
• Ex: Pesticides, pharmaceuticals,
plastics, pigments…(organic = Carbon)
–Estrogen in birth control pills is
affecting river life
• Causes genetic defects (see p.455, photos 20.8,
20.9)
• 2 main sources:
1. Improper disposal of
household/industrial waste
2. Runoff from fields, farms, etc.
Pollution Solutions
• Use less fertilizer (use
compost, leave clippings…)
• Establish buffer strips
• Keep livestock and feedlots
away from streams
• Perform crop rotation
–Corn   soybeans
• Use contour plowing
• Irrigate at night
• Use drip irrigation
Water Treatment
General Processes:
– Flocculation – use of a substance (ex: alum)
that causes precipitates to coagulate and settle
– Aeration – exposing the water to air
– Percolation – the process of water settling
through soil/gravel
• Removes the large stuff and some bacteria
– Disinfection – killing microorganisms prior to
discharge
• Done using UV light, O3 or Cl
Rural Sewage Treatment Septic tank and field
Municipal Treatment (1o, 2o, 3o)
• Primary:
– Uses grates/screens and a grit chamber/settling
tank to remove “solids”.
– “Solid” stuff is termed “primary sludge”. Mmmm.
• Secondary:
– Aerates the sewage
– Uses aerobic bacteria and protozoa to digest
organic matter.
• Tertiary:
– Uses binding agents, artificial wetlands, lagoons
to remove remaining impurities, esp. N and P
Municipal Sewage Treatment–
o
1,
o
2,
o
3
Good News!
• In spite of our growing
population, we use 10% less
water than we did in 1980
• Ex:
• Water saving toilets
• Low-flow shower heads
• Gray water, aka “sullage”
–Wastewater generated
from sink, washing
machine, etc. that can be
re-used.
Water Use and Waste
• #1 domestic use of water:
–Toilet. (40%)
• #2 domestic use of water:
–Shower/Bath (37%)
• Nearly ½ of industrial water is used for
cooling
–Wasted heat!
–Thermal pollution!
Water Use and Waste (cont.)
• #1 use of water
globally:
– Agriculture
• CA Central Valley:
– Subsidies covered
cost for distribution
– Farmers pay up to
1/10 of the actual
cost to supply the
water
– Incentive to
conserve….?
Want More Water? Cloud Seeding.
• Use of dry ice,
• Chemical is injected into
Potassium Iodide, silver cloud, forcing ice crystals
iodide, or hygroscopic to form, grow and fall
salts to get clouds to
release rain
• Issues:
– Loss of rain
elsewhere
– Contamination of
water
– Ecosystem disruption
Want More Water? Desalinate.
• Converts ocean or brackish water into
freshwater by removing salts
• Methods:
– Distillation
– Reverse osmosis (semi-permeable
membrane)
• 3-4x as expensive as other freshwater
• Energy intensive
• Saudi Arabia, Kuwait and United Arab
Emirates account for 85% of all
desalination plants
Glen Canyon Dam
Dams…Reservoirs…Channels
• Reservoir – a man-made basin for storage and
controlled release of water
• Disrupts terrestrial ecosystems
• Encourages agricultural development in areas
never meant to grow crops
• Massive water loss via evaporation and
seepage
• Evaporation and agricultural runoff change
the salinity of the water
Case Study: Colorado River
• Diversion of water from CO river
has caused fighting between CA, UT,
NV, AZ, NM and Mexico.
• Boulder dam and Glen Canyon Dam
– Block fish passage/spawning
– Trap nutrient-rich silt
– Alter water temperatures
• Farm irrigation has caused salts from naturally
alkaline soils to leach into river
• Millions of acres of farmland are “salt-poisoned”
due to irrigation using increasingly salty water
Case Study: Colorado River
What’s left for Mexico:
• CO River delta in Mexico (once lush, agriculturally
productive) no longer receives the natural flow of
silt and nutrient-rich water
• The salinity of the CO River was so high during the
1960s that Mexico !protestar!
– U.S. agreed to build a desalination plant to
restore the salinity of the CO to useable levels
Case Study: Aswan Dam, Nile R., Egypt
• Previously, the Nile River
annually overflowed its banks.
Effects:
– Deposition of 4 M. tons of
nutrient-rich silt on the valley
floor
– Made Egypt's otherwise dry
land productive and fertile
• But there were some years
when the river did not rise at
all, causing widespread drought
and famine.
• Aswan Dam created Lake
Nasser.
Aswan Dam
Benefits:
• Captures floodwater
during rainy seasons,
releases it during
times of drought.
• Generates enormous
amounts of electric
power
– More than 10 billion
kilowatt-hours/year
Aswan Dam
• Disadvantages:
– Nile River Delta region is no longer as
fertile/productive as it was:
Increased use of artificial fertilizers 
eutrophication…
– Tremendous social impacts
• Relocation of 1 M. Egyptian peasants to less
fertile government lands
• Loss to historians/archaeologists: Nubian
civilization is one of the world’s oldest. The
monuments/historical sites were flooded by
Lake Nasser.