Freshwater Resources Chapter 15. Ch 15 Freshwater Resources Rivers feeding estuaries are freshwater resources How do we use water? From where do we draw
Ch 15 Freshwater Resources Rivers feeding estuaries are
freshwater resources How do we use water? From where do we draw our
drinking water (we, us, here?) How does our use of freshwater
resources alter those systems? Why is our water supply dwindling?
How would you address this problem? Our freshwater is being
degraded. How has that happened? Are there solutions for mitigation
or restoration of those systems? How is wastewater treated?
Slide 3
Limited resource: only 2.5% of all water is fresh
Slide 4
Water is unequally distributed across Earths surface Different
regions possess vastly different amounts of groundwater, surface
water, and precipitation Many areas with high population density
are water- poor and face serious water shortages
Slide 5
Areas where water use exceeds supply
Slide 6
Some terms to guide your study Lentic waters-slow moving or no
moving waters-ponds, lakes, bogs, etc Lotic waters-moving
water-creeks, streams, rivers Floodplain-land within the
floodwaters of a river Watershed-all the land to one side of a fall
line that drains into a body of water; the area of land drained by
a river and its tributaries Aquifer-water trapped between layers of
rock or between layer of rock and clay Groundwater-water in aquifer
reservoirs Water table-upper limit of an aquifer Recharge an
aquifer-replace water lost or used in aquifer-water needs to
infiltrate land to recharge the aquifer Riparian = riverside areas
that are productive and species-rich
Slide 7
A typical aquifer
Slide 8
Freshwater wetlands Usually ecotones between aquatic and
terrestrial ecosystems Marsh-along edges of streams/rivers, may be
perched, may be tidal or nontidal, dominant vegetation is grass
Swamps-dominant vegetation is trees, water may be deep-a few feet
Bogs-shallow body of water covered with vegetation- frequently
sphagnum moss, can be over permafrost Prairie potholes-cyclical
nontidal marsh found in the Dakotas
Slide 9
Freshwater systems Water may seem abundant, but drinkable water
is rare Freshwater = relatively pure, with few dissolved salts Only
25% of Earths water is fresh Most freshwater is tied up in glaciers
and ice caps
Slide 10
How do we use water? From where do we draw our drinking water
(we, us, here?) Residential/municipal-10% of freshwater used
Industrial use-20% of freshwater used Agriculture-70% of freshwater
used (Ogallala aquifer) Arid countries use water for agriculture
Developed countries use water for industry Consumptive use:
irrigation, industrial, residential- water is not returned to
aquifer/surface waters Nonconsumptive use: hydroelectric dams some
industrial uses-returns water Our drinking water: CB, reservoirs,
rivers, aquifers, desalinization plants (reverse osmosis)
Slide 11
Ogallala Aquifer
Slide 12
How does our use of freshwater resources alter those systems?
Alter entire ecosystems: dams, canals, diversions Colorado river,
Yangtze river 60 % of the worlds largest 227 rivers have been
strongly or moderately affected Depleting surface waters-Aral sea
Irrigation (Salinization) Groundwater depletion Salt water
intrusion, sinkholes DEGRADATION
Slide 13
Plumbing the Colorado River The 2,330 km Colorado River begins
in the Rocky Mountains and trickles into the Gulf of California
Dams and irrigation provide water to millions of people in 7 states
Las Vegas, Nevada, is growing rapidly, and needs more water The
other states are allowing Las Vegas to drill for underground water,
even though it threatens the areas ecology and people
Slide 14
We divert and deplete surface water People have long diverted
water to farm fields, homes, and cities The once mighty Colorado
River has been extensively dammed and diverted
Slide 15
Can the Aral Sea be saved? People may have begun saving the
northern part of the Aral Sea
Slide 16
Yangtze River
Slide 17
Three Gorges Dam The dam, on the Yangtze River, is the largest
in the world 186 m (610 feet) high, 2 km (1.3 mi) wide Its
reservoir stretches for 616 km (385 mi) Provides flood control,
passage for boats, and electricity
Slide 18
A typical dam
Slide 19
Benefits and drawbacks of dams Benefits: Power generation
Emission reduction Crop irrigation Drinking water Flood control
Shipping New recreational opportunities Drawbacks: Habitat
alteration Fisheries declines Population displacement Sediment
capture Disruption of flooding Risk of failure Lost recreational
opportunities
Slide 20
Saltwater intrusion
Slide 21
Freshwater pollution sources
Slide 22
Water pollution Nutrient pollution-excess N and P Pathogens;
waterborne diseases: viruses, bacteria, protists (Giardia)
Biological hazards: giardiasis, typhoid, hepatitis A Toxic
chemicals (Cuyahoga river) Sediment loading Thermal pollution Point
vs nonpoint pollution
Slide 23
Nutrient pollution Pollution = the release of matter or energy
into the environment that causes undesirable impacts on the health
and well-being of humans or other organisms Nutrient pollution from
fertilizers, farms, sewage, lawns, golf courses Leads to
eutrophication Solutions Phosphate-free detergents Planting
vegetation to increase nutrient uptake Treat wastewater Reduce
fertilizer application
Slide 24
Sediment pollution Sediment can impair aquatic ecosystems
Clear-cutting, mining, poor cultivation practices Dramatically
changes aquatic habitats, and fish may not survive Solutions:
better management of farms and forests; avoid large-scale
disturbance of vegetation
Slide 25
Pathogens cause massive human health problems Currently, 1.1
billion people are without safe drinking water 2.4 billion have no
sewer or sanitary facilities Mostly rural Asians and Africans An
estimated 5 million people die per year Solutions: Treat sewage
Disinfect drinking water Public education to encourage personal
hygiene Government enforcement of regulations
Slide 26
Toxic chemicals From natural and synthetic sources Pesticides,
petroleum products, synthetic chemicals Arsenic, lead, mercury,
acid rain, acid drainage from mines Effects include: poisoning
animals and plants, altering aquatic ecosystems, and affecting
human health Solutions: Legislating and enforcing more stringent
regulations of industry Modify industrial processes Modify our
purchasing decisions
Slide 27
Cuyahoga River 1 of at least 13 fires
Slide 28
Indicators of water quality Scientists measure properties of
water to characterize its quality Biological indicators: presence
of fecal coliform bacteria and other disease-causing organisms
Chemical indicators: pH, nutrient concentration, taste, odor,
hardness, dissolved oxygen Physical indicators: turbidity, color,
temperature
Slide 29
Groundwater Any precipitation that does not evaporate, flow
into waterways, or get taken up by organisms Groundwater makes up
one fifth of the Earths freshwater supply Groundwater becomes
surface water through springs or human-drilled wells Groundwater
may be ancient: the average age is 1,400 years
Slide 30
Groundwater pollution Doesnt flush Persistent toxins trapped No
O2, low microbes, low organic material decomposition SLOW Some
toxics naturally occurring, Fl in Smithfield, Al, NO3 (causes
cancers, miscarriages, blue-baby syndrome), SO4, As Anthropogenic
sources: industrial, agricultural and urban wastes Heavy metals,
petroleum products, industrial solvents, pesticides, pathogens
(E.coli), BOCs, leakage from landfills, leakage from septic tanks,
industrial chemical tanks, gas and oil tanks
Slide 31
Climate change will cause water shortages Climate change will
cause Altered precipitation patterns Melting glaciers Early season
runoff Intensified droughts Flooding Increasing probability that
there will be still less water for more people Even if water stays
the same, the population doesnt-7 billion people now populate the
Earth
Slide 32
Are there solutions for mitigation or restoration of those
systems? Use less use less use less use less Dont pollute from the
beginning Legislation has reduce point source pollution Clean water
act Lowering demand Politically difficult in the short term Offers
better economic returns Causes less ecological and social damage
Increasing supply Water can be transported through pipes and
aqueducts It can be forcibly appropriated from weak
communities
Slide 33
Agricultural demand can be reduced Look first for ways to
decrease agricultural demand Lining irrigation canals Low-pressure
spray irrigation that spray water downward Drip irrigation systems
that target individual plants Match crops to land and climate
Selective breeding and genetic modification to raise crops that
require less water
Slide 34
Residential demand can be reduced Install low-flow faucets,
showerheads, washing machines, and toilets Water lawns at night,
when evaporation is minimal Eat less meat Xeriscaping = landscaping
using plants adapted to arid conditions
Slide 35
Industrial demand can be reduced Shift to processes that use
less water Wastewater recycling Excess surface water runoff used
for recharging aquifers Patching leaky pipes Auditing industries
Promoting conservation/education
Slide 36
Economic approaches to water conservation End government
subsidies of inefficient practices Let the price of water reflect
its true cost of extraction Industrial uses are more profitable
than agricultural Less developed countries suffer Privatization of
water supplies May improve efficiency Firms have little incentive
to provide access to the poor Decentralization of water control may
conserve water Shift control to the local level
Slide 37
It is better to prevent pollution It is far better to prevent
groundwater contamination than correct it Other options are not as
good: Removing just one herbicide from water costs $400 million
Pumping, treating, and re-injecting it takes too long Restricting
pollutants above aquifers would shift pollution elsewhere Consumers
can purchase environmentally friendly products Become involved in
local river watch projects
Slide 38
Treating wastewater Wastewater = water that has been used by
people in some way Sewage, showers, sinks, manufacturing, storm
water runoff Septic systems = the most popular method of wastewater
disposal in rural areas Underground septic tanks separate solids
and oils from wastewater The water drains into a drain field, where
microbes decompose the water Solid waste needs to be periodically
pumped and landfilled
Slide 39
Municipal sewer systems In populated areas, sewer systems carry
wastewater Physical, chemical, and biological water treatment
Primary treatment = the physical removal of contaminants in
settling tanks (clarifiers) Secondary treatment = water is stirred
and aerated so aerobic bacteria degrade organic pollutants Water
treated with chlorine is piped into rivers or the ocean Some
reclaimed water is used for irrigation, lawns, or industry
Slide 40
A typical wastewater treatment facility
Slide 41
HRSD
Slide 42
HRSD: Hampton Roads Sanitation District 9 major treatment
plants 231 million gallons per day Wastewater flows from municipal
piped systems to HRSDs interceptor system of pipes and pump
stations to our treatment plants. One of my former students is a
scientist with HRSD. He samples water throughout the district for
toxins.
Slide 43
Waste Water Treatment Preliminary Treatment: Removes grit
(sand), debris, and manmade objects. Primary Treatment: Allows for
the settling and flotation of organics and solids. Heavy solid
particles such as food waste sink to the bottom, and lighter
organics such as oil and grease float to the top. About 35% of the
organics and 50% of the solids are removed. Secondary Treatment:
Uses naturally occurring microorganisms to remove additional
organics and solids such as sugars, starches, proteins, detergents,
and soaps. Nutrient Removal: Eliminates at least 2/3 of the
phosphorus and 1/3 of the nitrogen from wastewater. Those treatment
plants with Biological Nutrient Removal eliminate an additional 1/3
of the nitrogen. Disinfection: Kills disease-causing bacteria.
Effluent is typically chlorinated and then dechlorinated before it
is released to local waterways, making it safe for aquatic
life.
Slide 44
Artificial wetlands Natural and artificial wetlands can cleanse
some waste water After primary treatment at a conventional
facility, water is pumped into the wetland Microbes decompose the
remaining pollutants Cleansed water is released into waterways or
percolated underground Constructed wetlands serve as havens for
wildlife and areas for human recreation More than 500 artificially
constructed or restored wetlands exist in the U.S.
Slide 45
Lake and pond zonation Benthic zones: Littoral Sublittoral
Profundal Limnetic, pelagic zones Epilimnion (mesolimnion)
hypolimnion
Slide 46
Lake Classification Trophic ClassificationNutrient
concentrationBiological productivity OligotrophicLow
MesotrophicModerate EutrophicHigh hypereutrophicExtremely highVery
high