Water Availability in the Hydrologic Cycle

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Water Availability in the Hydrologic Cycle
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Fig. 6.01
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Table 10.01
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US Hydrologic Water Budget

• Next slide billions of gallons per day

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Fig. 10.18
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Precipitation East vs West
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Fig. 10.19
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US Water Withdrawals

• Next slide millions of gallons per day from
  both ground water and surface water sources.

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Fig. 10.20
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Fig. 10.21
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Fig. 10.22
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Ogallala Aquifer

• Over irrigation (ground water mining)

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Fig. 10.27
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Colorado River Diversions
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Fig. 10.26
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Fig. 10.31
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Water Quality

• Concentration amount of solute divided by
  amount of solvent.
• m-mass (mg-milligram) V-volume (L-liter)
• m/V example mg/L
• m/m example mg/kg
• ppm parts per million mg / kg
• note ppm mg/L ASSUMING 1L 1 kg

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Measures of Water Quality

• TDS concentration of Total Dissolved Solids
• pH (hydrogen ion concentration)
• Concentrations of major ions
• Concentrations of contaminants (ideally low)
• DO Dissolved Oxygen
• BOD / COD Biological Oxygen Demand / Chemical
  Oxygen Demand the amount of organic matter in
  water (oxygen required to respire organic matter

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Total Dissolved Solids (TDS)

• Usually measured in parts per million (ppm), e.g.
  mg / kg, because 1 Liter of solvent does NOT
  equal 1 kg
• 500 ppm or less is ideal
• lt1000 ppm is potable (acceptable for drinking)
• 1000 to 10,000 ppm is saline
• 31,000 ppm is seawater
• 10,000 to 100,000 (or over!) is called brine

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pH

• Measure of the excess acid (lt7) or base (gt7) in
  the water.
• Acid H
• Base OH
• Slightly basic (7 to 7.5) is best
• --Neutral is 7
• --alkalinity is a term for basic solutions, but
  is actually the sum of non-conserved ions (the
  sum of bases, mostly HCO3, minus sum of acid)

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Major Ions

• Cations
• Na, K
• Ca, Mg
• Fe, Mn
• Anions
• Cl
• HCO3
• SO4

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Fig. 10.01 p.242
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Sum of concentrations TDS

• Major ions constitute over 98 dissolved
  chemistry in natural ground waters.
• Example Na in 8 oz. Diet Pepsi serving 25
  mg
• Na 105 mg / L 105 mg/kg (assuming 1 L 1
  kg)
• 105 ppm
• Thats just sodium! Now add other 8 major ions
  for TDS!!!
• Compare to 6 ppm for average river water! (next
  slide)

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Table 10.03
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Dissolved Oxygen

• Concentration of dissolved oxygen in water
• Essential for living organisms
• High DO is preferable
• the higher the T, the lower the DO (we discussed
  thermal pollution already)
• The higher the BOD / COD, the lower the DO

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BOD / COD

• Measure of organic matter in water
• (We discussed nutrient pollution gt organic
  matter relation already)
• COD measures oxygen required to oxidize organic
  matter chemically
• BOD measures oxygen required to respire
  (bio-oxidize) organic matter
• Analytically measured with oxidizing agents