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Unit 6 - Topic 4 Water, Food Production Systems & Society (4.1 -…

- - - - About 2.6% is fresh water
        
        About 68.7% of this water is found in polar ice caps and glaciers
        
        30.1% is in ground water
        
        Only 0.3% of the water in Earth's surface is in lakes, rivers, and swamps
        
        The other 0.9% is not mentioned in the textbook
      - 97% is ocean (salt) water
  - - - Transfers (same state) include:
        
        Advection (wind-blown movement)
        
        Flooding
        
        Surface Run-off
        
        Infiltration and percolation (when water runs into and through soil or rocks)
        
        Stream flow and current
      - Transformations (change state) include:
        
        Evapotranspiration - liquid to water vapour
        
        Condensation - water vapour to liquid
        
        Freezing - into solid snow or ice
      - Storages include:
        
        Oceans
        
        Soil
        
        Groundwater (aquifers)
        
        Lakes
        
        Rivers and streams
        
        Atmosphere
        
        Glaciers and ice caps
    - - Humans have changed the landscape and interrupted the movement of water by
        
        Withdrawals - for domestic use, irrigation in agriculture, industry
        
        Discharges - by adding pollutants to water, eg chemicals from agriculture, fertilizers, and sewage
        
        Changing the speed at which water can flow and where it flows
        a) In cities by building roads and channeling rivers underground or in concreted areas
        b) Canalizing: straightening large sections of rivers in concrete channels to facilitate more rapid flow through sensitive areas.
        c) With dams, barrages, and dkyes, making reservoirs
        
        Diverting rivers or sections of rivers
        a) Many are diverted away from important areas to avoid flood damage
        b) Some are diverted towards dams to improve storage
      - Examples of major changes caused by humans
        
        Aral Sea - intense irrigation has almost stopped river flow into the sea and lowered the sea's level (shrunk in area by 90% in the last 50 years)
        
        Ganges Basin - deforestation increases flooding as precipitation is not absorbed by vegetation
        
        Run-off from urbanized areas causing local flooding
      - Urbanization and flash floods
        Flash floods occur when rainfall or snowmelt cannot infiltrate the soil and runs off the surface. This could be due to the land being hard-baked in hot, dry areas, but more and more is due to impermeable surfaces in cities
  - - - Surface Currents:
        
        Upper 400 m of ocean
        
        Moved by the wind
        
        Earth's rotation deflects them and increases their circular movement
      - Deep Ocean Currents:
        
        Also called thermohaline currents
        
        Make up 90% of ocean currents
        
        Causes the oceanic conveyor belt
        
        Due to differences in water density caused by salt and temperature
        
        Warm water can hold less salt than cold water, so it's less dense and rises
        
        Cold water can hold more salt, making it denser, causing it to sink
        
        When warm water rises, cold water has to rise up to replace it
        
        This is called an upwelling
        
        When cold water rises, it has to be replaced by warm water
        
        This is called a downwelling
        
        Water circulates in this way
        
        Cold Ocean Currents
        
        Run from the poles to the equator
        
        Examples:
        
        Humboldt Current
        
        Benguela Current
        
        Warm Ocean Currents
        
        Run from the equator to the poles
        
        Examples:
        
        Gulf Stream
        
        Angola Current
    - - Oh God it's chemistry
        
        Water has a higher specific heat capacity than land. This means that it takes more energy to heat up water by one degrees Celsius than it does to heat up the ground
        
        This also means that water heats up and cools down a lot slower than land masses. This leads to maritime climate patterns, where you have cooler summers and warmer winters
      - Ocean currents also affect local climate
        
        The warm Gulf Stream/North Atlantic Drift moderates the climate of Northwestern Europe, which otherwise would have a sub-arctic climate
        
        The cold Benguela Current, under the influence of prevailing southwest winds, moderates the climate of the Namibian desert
        
        The Humboldt Current impacts the climate in Peru
- - - - Domestic: used for drinking, cooking, and cleaning
      - Agriculture: irrigation + animals to drink
      - Industry: manufacturing, mining, etc
      - Energy: hydroelectricity + cooling of generators
      - Other Activities: marking borders + transportation (over bodies of water
      - HOW MUCH WATER DO WE NEED
        Estimate that each person only needs 20-40L per day, but some countries are using >100L whereas others have access to <20L
  - - - Aquifers:
        
        Layer of porous rock (holds water) sandwiched between impermeable rock
        
        Accessed through wells
        
        Often unsustainably used as many aquifers cannot be replenished or replenish at a very slow rate (some as slow as 1-10m per century)
      - Surface Water
        
        pumped from streams, lakes, rivers, etc
        
        can be renewable, but may be nonrenewable due to scarce precipitation
    - - ISSUES
        
        Climate change leads to changes in rainfall patterns
        
        Many major rivers are becoming no more than streams
        
        Sedimentation occurs from low water flow; river gets shallower as sediment stays stationary instead of moving downstream
        
        Excessively high pumping rates for aquifers + leads to soil caving in (potentially destruction of buildings)
        
        Contamination of freshwater makes it unusable (from fertilizers + industries)
        
        Irrigation degrades the soil (especially in dry areas) by salinization (water evaporates too quickly so dissolved minerals stay on the surface)
        
        Warm water from industry plants hold less oxygen so are harmful
      - SOLUTIONS
        
        Use reservoirs, redistribution, desalination, rainwater harvesting, and artificially replenishing aquifers
        
        Use water efficient appliances in the home
        
        Car washes should be in a closed water system (no pollution by oil)
        
        Recycle/reuse greywater (wastewater without feces)
        
        Use drought resistant crops + better irrigation (closed pipes, trickle system, subsurface irrigation)
        
        Reduce pesticide + fertilizer use
        
        Use organic fertilizers instead of chemical ones
        
        Mandatory for industries to remove pollutants before release
        
        Cool industrial wastewater before release through evaporation
- - - - Creates Shallow Water
        
        has 50% of oceanic productivity but 15% of its area
        
        upwellings bring nutrient-rich water up to the continental shelf
        
        light reaches the shallow seas so producers can photosynthesize
        
        countries can claim it as theirs to exploit and harvest
    - - Marine above the Continental shelf = higher productivity
        
        Deep oceans where light does not reach = low productivity
        
        Only food sources are chemotrophs and dead organic matter that descends from above (marine productivity above the continental shelf)