WATER RESOURCES

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WATER RESOURCES
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Water we waste it, we pollute it, we take it
for granted. Virtually the most valuable
commodity we have (along with O2 )
You're about 70 Water!
Tree 60 water Jelly fish 90 water
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The water planet
Water
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All of the Earth's waters are circulated by the
HYDROLOGIC CYCLE
Water moves through the hydrologic cycle at
various speeds. For example 40,000 years to
recycle oceanic water 2 weeks to recycle river
water 9 to 10 days to recycle atmospheric water
Where has your water been?
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The hydrological cycle
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Evaporation

• Injects water vapour into atmosphere
• Uses 50 of energy at earths surface (cools the
  earths surface)

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The Atmosphere

• only 0.001 of all water
• links major water stores
• evaporation
• condensation
• precipitation
• cold air hold less water than hot air
• as hot air rises and cools, precipitation can
  form returning water to the earth or oceans

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Rain doesnt always make it to the earth
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Rain doesnt always make it to the earth
Interception loss may be 20 40 of total
rainfall for forests
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Snow can turn into glaciers and remain on land a
long time
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Antarctic ice photo by Megan Balks, Waikato
Univ.
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Rain that does make it to the earth can do
several things
infiltration
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About 10 of precipitation will infiltrate the
soil and rock to become groundwater, forming a
water table.
The majority of accessible fresh water is
groundwater, water beneath the Earth's surface.
Water saturated permeable rock is an aquifer.
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Aquifers
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Rivers return water from the land to the ocean
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Waimakirri River, New Zealand
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The Water Balance

• May be applied to whole river basins or
  catchments (watersheds)

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Quantifying the hydrological cycle
Rainfall to a watershed P 15 mm
Evapotranspiration E -4 mm Discharge in stream
Q -6mm Change in storage Q 5mm
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Rivers
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Boreal stream with organic acids flowing north
to the arctic
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Most of earths water is in the oceans
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Running the hydrological cycle takes energy!
Most of the energy for the hydrologic cycle comes
from the sun
Water in the atmosphere helps trap heat (H2O is
a greenhouse gas) and distribute heat
The hydrologic cycle is the main global energy
redistribution system -thru both the oceans
and the atmosphere
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Ocean currents
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The hydrological cycle
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Titan methane cycle
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Global Water Supply

• ONLY 0.01-0.03 of worlds water is readily
  available
• AND this is NOT evenly distributed
• (many water-poor countries in the middle east)
• Human water use has increased 4-fold in the last
  50 yrs!
• increasing population and
• increasing use per person
• Approximately 70 of water used is for Agriculture

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Irrigation
- The BIGGEST water use

• 1950 -80 world irrigation area tripled
• 1990 7 less irrigated area per person than
  1980
• increased competition between rural and urban
  water use
• 21 of USA crop irrigated by draw-down of water
  table

This is NOT SUSTAINABLE
26 of world irrigated area suffers waterlogging
and salinization
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The Ogallala Aquifer
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Two main problems associated with groundwater
usage Withdrawal can result in depletion
(removal of water from aquifers faster than it
can be replaced) land subsidence salt water
intrusion Discharge can pollute groundwater
(groundwater is very vulnerable to pollution
which can be very costly and difficult to clean)
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Dams and Canals redistribute water from areas
of water surplus to water deficit areas
Dams are built to minimize flood damage, store
water, or provide hydroelectric
power Environmental impacts of dams include
sediment accumulation, downstream scouring, water
loss from evaporation, salinization, biological
disturbance
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sinks
sources
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Water Resources
Environmental costs are typically excluded
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There are many areas where water is scarce!
McKinney and Schoch, 2003
Political and Economic solutions may be needed to
effectively use our water Laws now protect some
surface and groundwater, but this is not true
everywhere Water for agricultural use is
subsidized--no incentive to conserve
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There are many ways to increase efficiency in
our use of water
Microirrigation for agriculture Individual
lifestyle conservation shorter showers dont
let the water run low-flush toilets Xeriscaping W
astewater reclamation
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Water use
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WATER SAVINGS GUIDE
Activity Conservative use - saves water Normal use -- wastes water
Shower Wetdown/rinse off 4 gallons Regular shower 25 gallons
Brushing teeth Wet brush, brief rinse 1/2 gal. Tap running 10 gallons
Toilets Minimize flushing, low-flush toilets Old toilet, frequent flushing?!?!
Leaks Report ASAP A small drip 25 gallons per day
Energy Turn off power Wasting energy wastes water
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• Key Points
• Water circulates among the atmosphere, rivers,
  oceans, groundwater, glaciers and other
  locations through the hydrological cycle
• The hydrologic cycle is powered by the sun it
  is a major way that global energy is
  redistribution
• Liquid Fresh water is a very small amount of
  the worlds total water supply (0.6 with only
  lt0.03 readily available)
• Demand for fresh water is increasing,
  particularly for agriculture which uses most of
  the consumed water
• Water is not equally distributed throughout the
  world and conservation measures will become
  increasingly important as water demand
  increases and conflicts for water use increase

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