APES CH 7

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APES CH 7

• Water, Hydrologic Cycle and Human Use

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• Water
• fundamental to life
• 71 of Earths surface is covered with water
• 97.5 is salt water (oceans)
• 2.5 of all water is fresh water
• of this 2.5 2/3 is bound up in the polar ice
  caps and glaciers
• only .77 of all water is found in lakes,
  wetlands, rivers, groundwater, biota, soil and
  the atmosphere.
• All the freshwater is supplied by evaporation
  from oceans.

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• From the freshwater, all water for industrial,
  agricultural, and personal use is obtained.
• All freshwater habitats for aquatic plants and
  animals

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Water moderates the climate

• Vast currents, such as the Gulf Stream,
  transport warm water from the equator to higher
  latitudes and cold water from the poles to the
  tropics.

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• In developed countries humans have created a huge
  infrastructure to control water.
• Irrigation water towers pipelines
• dams desalination plants
• canals treatment plants

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• In developing countries, over 1 billion people
  still lack access to clean drinking water.
• 3 million deaths traced to waterborne diseases
• environmental disasters because of the attempt to
  control water
• freshwater is a limiting resource in many parts
  of the world.

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The Hydrologic Cycle
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• Water rises to the atmosphere through
• evaporation
• transpiration
• Water returns to the land and oceans through
• condensation (dew, frost)
• precipitation

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Unique Properties of Water

• Weak Hydrogen bonds hold water molecules together
• below 0ºC, the kinetic energy of the molecules is
  low, the H bonds are strong enough to hold the
  molecules in place with respect to one another.
  (ice)
• Above 0ºC and below 100ºC, the kinetic energy of
  the molecules is such that H bonds break and
  reform with different molecules, (liquid water)
• as water molecules gain kinetic energy (from the
  sun or other source) molecules break free -
  evaporation

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• Water vapor in the air-
• humidity
• generally measured as relative humidity, a
  percentage of what the air can hold at a
  particular temp. 60 relative humidity means the
  air is holding 60 of the water it CAN hold.
• warmer temps, hold more water
• cold air is DRY,
• if warm air is cooled, the relative humidity
  rises until it reaches 100. At that point,
  water begins to condense back to a liquid (a
  cloud).

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• Water vapor varies by volume in the atmosphere
  from a trace to about 4. Therefore, on average,
  only about 2 to 3 of the molecules in the air
  are water vapor molecules. The amount of water
  vapor in the air is small in extremely arid areas
  and in location where the temperatures are very
  low (i.e. polar regions, very cold weather). The
  volume of water vapor is about 4 in very warm
  and humid tropical air.

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• Condensation
• The opposite of evaporation
• Happens when water molecules rejoin by H bonds
• Cloud, fog
• Dew
• Facilitated by aerosols, condensation nuclei
• Dust, salt from oceans, volcanic ash
• Anthropogenic sources, pollution

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• Purification
• Evaporation and condensation purify water
  naturally
• Water in the atmosphere turns over every 10 days.
• The source of all the natural fresh water on Earth

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• Precipitation
• Warm air rises from Earths surface, encountering
  lower atmospheric pressures, the air expands and
  cools, adiabatic cooling.
• Produces clouds
• When cool air descends and is compressed due to
  higher pressures near the surface, the air warms
  (not due to any addition of energy), adiabatic
  warming

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• Most precipitation in any given area on Earth is
  affected by rising air.
• Affected by global convection currents
• Rain shadow
• Earth is heated most directly and continuously
  over the equator.
• Air rises, cools adiabatically, condensation
  occurs, precipitation.
• This process is repeated often
• Supports tropical rain forests

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Air rising near the equator produces the heavy
rains associated with rainforests. Descending
air between 25 and 35º N and S is dry. This
produces the worlds deserts.
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Because Earth rotates, the wind flows in a
westerly direction.
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• Rain shadow
• Moisture laden trade winds encounter mountain
  ranges. Air cools as it is deflected up over the
  mountain range.
• The air mass loses its moisture.
• When it is on the leeward side of a mountain, the
  air is dry.

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• After glaciers which hold 90 percent of fresh
  water (2.4 of all water), the next largest
  reservoir of fresh water is held in the ground as
  groundwater.
• Water that does not evaporate or runoff
  infiltrates. Upper soil layers that hold both
  air and water make up the zone of aeration. (this
  is where moisture for plants comes from)
• Soil layers where all spaces are filled with
  water make up the zone of saturation. The top of
  this zone is the water table.

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• Groundwater
• Enters the ground through infiltration
• Infiltration
• The amount that soaks in compared with the amount
  that runs off, infiltration runoff ratio
• Runoff that flows over the surface
• Watershed, water ends up in rivers, lakes and
  streams.

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• Water that infiltrates
• may be held in the soil
• depends on water holding capacity of the soil
• capillary water - may be absorbed by plant roots,
  green water
• Percolation
• blue water flow
• water not held in soil
• gravitational water
• encounters a layer of rock or clay aquiclude or
  aquatard
• becomes groundwater
• upper surface the water table

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• Wells are dug to below the water table
• aquifer - layer of porous material through which
  groundwater moves
• aquifers hold 99 of liquid fresh water
• may be found at various depths between layers of
  impervious rock
• recharge area - area where water enters an
  aquifer.

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• Purification
• as water percolates through soil
• debris and bacteria filtered out very important
• minerals may be dissolved in ground water
• groundwater generally safe for drinking
• exceptions -
• minerals containing sulfides, arsenic or other
  poisonous elements
• areas where ground water intersects with
  contaminated water
• spring
• where the water table finds an opening to the
  surface

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Human impacts on hydrologic cycle

• Changes to Earths surface
• as forests cleared or land overgrazed
• water runs off instead of percolating into the
  groundwater
• floods - increasing because of deforestation and
  cultivation
• means less infiltration, less evapotranspiration
• less groundwater recharge

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• changes to Earths climate
• groundwater is actually fossil water
• left over from a cooler wetter time
• Earths climate warming
• means more evaporation from land and water bodies
• should lead to heavier precipitation
• more flood events
• should generate more hurricanes
• more drought

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• atmospheric pollution
• aerosol particles form condensation nuclei
• anthropogenic aerosols in the increase
• sulfates, carbon
• solar radiation reduced (cooling effect)
• suppresses rainfall (even though they encourage
  cloud formation
• because rainfall is suppressed, the aerosols
  remain in the atmosphere longer

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• withdrawals for human use
• causes depletion of groundwater
• leads to unique problems

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Water A Resource to Manage

• Consumptive
• irrigation and agricultural use - 70
• Nonconsumptive
• electric power production
• industrial use
• residential use - 10

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• Sources
• for domestic water,
• groundwater sources 53
• surface water 47
• In the developing countries
• surface water and shallow wells receive runoff
• polluted - animal wastes, human sewage likely to
  contain pathogens
• sometimes the only water available responsible
  for the deaths of over 3 million people per year
  - 90 children

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• In the US - along the Mississippi
• water used, treated, put back in, used, treated,
  many times
• not the case in developing countries, each city
  downstream has more and more pollution to contend
  with
• smaller public drinking water systems, frequently
  rely on groundwater
• minimally treated
• replenished through the water cycle

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• Dam impacts
• loss of riverine habitats
• loss of waterfalls, rapids,
• fish runs
• 95 of salmon juveniles die on the way to the
  ocean
• wildlife that depend on water or food chains
  adversely affected
• wetlands along rivers damaged

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• Dam problems
• With a dam, disruption off river systems
• Broken up into fragments
• Attempts to restore rivers by removing dams cause
  other problems
• Dams cause silt and sediment to build up
• In Mass. Attempts to restore the Blackstone
  River was stopped other things are being done
  since your book was printed.
• Sediments contain heavy metal
• Attempts to protect wild rivers with Wild and
  Scenic Rivers Act

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• Removing dams has its own problems
• Sediments have build up behind the dam
• Sometimes this sediment contains toxic chemicals
  and heavy metals. And prohibits the removal of
  the dam.

http//www.blackstoneriver.org/programs/Blackstone
_River_ Fish_Passage_Project.php
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Ways the fish ladders have benefitted the
environment

• Forage for valuable commercial and recreational
  fish species such as bluefish, striped bass, bass
  and pickerel
• Restoration of anadromous fish to the Blackstone
  River would provide substantial ecological
  benefits for the Blackstone River watershed and
  the Narragansett Bay Ecosystem, as well as
  economic benefits for the communities of the
  Blackstone Valley and beyond. Specifically, the
  re-established fish runs would provide
• Forage for predatory birds such as waterfowl,
  wading birds, and osprey
• Enhanced fishing opportunities for urban anglers
• Educational opportunities and aesthetic benefits
  to visitors at Slater Mill and other areas
• Enhanced opportunities for tourism and recreation
  in the Blackstone River Valley Heritage Corridor

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• Estuaries
• Fresh water mixes with salt water in estuaries to
  produce some of the most productive ecosystems on
  Earth.
• Breeding grounds for fish, shellfish, waterfowl
• If water is diverted from rivers, less gets into
  the estuary. Less flushing of the estuary. Salt
  content increases. Ecosystems collapse.
• Read p 194, CALFED Bay Delta Program

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• Groundwater
• Ogallala aquifer supplies irrigation to 10.4
  million acres
• Mostly fossil water
• Withdrawal rate 28 billion cubic meters per year.
  
• Two orders of magnitude higher than the recharge
  rate
• Water tables dropped 100-200 ft.
• Lowering at 6 ft per year.
• This groundwater considered nonrenewable
• Recharge rate is in the hundreds of years.
• Much land unfarmable due to lack of irrigation

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Ogallala Aquifer
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• Surface waters
• Also affected by the falling water table
• Loss of wetlands
• Land subsidence
• In the San Joaquin Valley as much as 29 feet.
• Sinkhole underground cavern filled with water,
  loses its water and collapses.
• A problem in SE US. Alabama, Fl
• Mexico City has been subsiding since Aztec times.
  Because of population growth and urbanization,
  and overdrafts, some of the city as sunk as much
  as 8.5 m in recent times.

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• Saltwater Intrusion
• Also due to dropping water table in coastal
  regions

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Water Stewardship Public Policy Challenges

• There is enough water for the world.
• The problem is, the water is not distributed
  where it is most needed
• All water has been recycled countless times.
• So whats a citizen to do?
• Capture runoff
• Gain better access to existing groundwater
  aquifers
• Desalt seawater desalination
• Conserve present supplies by using less water
• Plant native plants that are ecologically in
  harmony with the surroundings
• The largest domestic use or water is toilet
  flushing.
• Use low volume toilets
• Residents of Queensland AU and Singapore are now
  drinking purified sewage effluent.

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• Plant native plants that are ecologically in
  harmony with the surroundings
• The largest domestic use or water is toilet
  flushing.
• Use low volume toilets
• Dual plumbing in new construction of homes and
  commercial buildings
• Residents of Queensland AU and Singapore are now
  drinking purified sewage effluent. remember
  water in nature has been recycled many, many
  times

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• Tapping more Groundwater
• Groundwater depletion considered biggest threat
  to irrigated agriculture
• Being polluted by fertilizers, pesticides, animal
  wastes, industrial chemicals

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• Desalting Seawater
• This provides much water for countries of the
  Middle East
• 2 technologies Reverse osmosis, distillation

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• Using less water
• How best to use water without depleting
  groundwater resources
• surge flow for irrigation systems
• Periodic flow instead of continuous flow
• Much loss of water through evaporation
• Drip irrigation
• Very high cost
• Crops actually grow better than using traditional
  methods

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• Treadle pumps
• Small scale irrigation in developing countries

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• Municipal systems
• Design landscaping with xeriscaping
• Use of 1.6 gallon toilet
• Gray water
• Use of slightly dirtied water from sinks showers,
  bathtubs, laundry tubs for use to flush toilets,
  wash cars, water golf courses, water lawns

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• What can we expect in the future?
• Any fresh water source must be divided to serve
  the needs of natural ecosystems, agriculture,
  industry an domestic needs of humans
• humans use 26 of total terrestrial
  evapotranspiration
• 54 of accessible precipitation runoff

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• Water Wars
• So CA depends on the CO river for water for
  irrigation of the Imperial Valley as well as
  drinking water for large cities (LA)
• recently a deal was made to divert 65 billion
  gallons/year to San Diego for domestic use.
• For this the city will invest 2 billion
• this will remove 20,000 acres out of 150,000 from
  irrigation
• normally the irrigation water drains into the
  Salton Sea (CAs largest lake) which provides the
  freshwater for the sea
• sea provides habitat for fish and waterfowl

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• EPA
• oversees the nations water quality.
• Clean Water Act authorize the EPA to develop
  programs and rules to carry out its mandate
• No federal bureaucracy oversees water quantity

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• There needs to be a national policy to guide
  local and state decisions.
• Key Issues
• Water efficiency
• water should be priced according to its real
  cost. No subsidies.
• Polluters charged according to their effluents.
• Watershed management must be integrated
• The US must respond to the global water crisis -
  safe drinking water
• US must take action to reduce the emissions of
  greenhouse gases (join the Kyoto Accord)
• Data must be kept on recharge and withdrawal from
  aquifers, streams and rivers.

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• We must learn to manage the water our planet has.
• The problem is not that there is too little
  freshwater
• we need to manage the water that we have.
• Water is everybodys business