Water is fundamental to life
A human baby is
75% water
Water is used in chemica
l reaction
s
Water moves up 300’
tall plants
Water regulates
temperature
What do you know about water chemistry? The ends are
charged
Its POLAR
2. Capillary action: cohesion=surface tension
adhesion= sticks to surface
5. Universal Solvent
3. Expands when frozen
1. Polar molecule: attracts other polar molecules
4. High specific heat
Water’s unique properties
Geographic factors determine precipitation amounts
I. Proximity to water sourceII. Global Wind patternsIII. Topography : Mountains create
rain-shadows
Dew Point= Temperature
where the condensation
exceeds evaporation and
condensation occurs
Mass of water vapor divided by mass of dry air = absolute
humidity
absolute humidity to maximum potential
humidity in air = relative humidity
How much water is available for our use? Of the 2.5% freshwater 1.7% ice: unavailabe 0.7% surface waterMarine water = 97.5%Fresh water = 2.5%
How can you define where a watershed is located?
a. Topographyb. Where the water collectsc. Where the water exits
The Oceans are a Major Water CompartmentThe oceans hold 97% of all liquid water on
the earth.90% of the earth’s biomass is found in the
oceans.The oceans play a major role in moderating
earth’s climate.Ocean currents moderate the climate by
redistributing warm and cold water around the earth like a global ocean conveyor belt.
Community’s water sourceGeographical vs. Political BoundariesHow many bathtubs did it rain last night?
What controls how much water flows in a stream (watershed)? Precipitation: Infiltration:
Shallow: moves to streamDeep: moves to groundwater
Soil characteristics Soil saturation Land cover Slope
What are the effects of increased run-off to a stream?
Sediment load Reduced lightChanges substrateIncreased PM
Increased velocityErodes river banks
Increased nutrients Eutrophication
Less available waterConflicts over water use
Personal water use Global average : 1,385 m3 / yr; A person needs 2.5 qts per day (from all sources)
Water trivia facts How much does it take to produce one ton of
steel?62,600 gallons How much water does it take to process one
chicken?11.6 gallons
Demand for water is specific, availability is not
Consumptive or Withdrawal?
Consumptive water, according to the text is water that is made unavailable for human use due to evaporation, tied up in plants or animals, chemical changes,
Renewable water is the total of readily available surface and groundwater minus evaporation.
Water scarcity = demand exceeds availableWater Stress = Water scarcity + increased competition for demand.
Conflicts in water valueAgricultural demand
Aral sea: CA
Lake Owen dried up by1924
Lake Mono lost 41% of its volume between 1941 & 1982 Today the San Joaquin valley is in jeopardy
Land subsidence The San Joaquin Delta, produces 25 %of the nation’s table food on only 1 % of the country’s farmlandThe maximum subsidence, near Mendota, was more than 28 feet.Subsidence has slowed or reversed because surface water is being pumped in
Porosity: volume of all of the open spaces Material Porosity (%)
well-sorted sand 25-50
sand and gravel 20-35
clay 33-60
Groundwater Stores Large Water ResourcesAquifers - porous layers of sand, gravel, or
rock lying below the water tableArtesian - Pressurized aquifer intersects
the surface (water flows without pumping).
Recharge zones - area where water infiltrates into an aquiferRecharge rate is often very slow.
Presently, groundwater is being removed faster than it can be replenished in many areas.
Ground Water Compartments Ground water is the second largest
reservoir of fresh waterInfiltration - process of water percolating
through the soil and into fractures and permeable rocksZone of aeration - upper soil layers that hold both air and water
Zone of saturation - lower soil layers where all spaces are filled with waterWater table - top of zone of saturation