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ITEM 88-Anna,Katrina,Doll - Coggle Diagram

- - - - Limit penetration of sunlight.
        Measured by optical instruments or Secchi disc.
        
        Instructions to use Secchi disc:
        
        Lower the disc under water until it disappears.
        
        Read the depth and raise the disc to become visible.
        
        Read the depth and calculate average depth.
        
        Stand or sit on the board.
        
        Wear glasses and work on the shady side of the boat.
  - - - Factors affect flow velocity:
        
        Time: melt water, high flow rates, summer drought low flow rates.
        
        Depth: surface water flows more slowly than in the middle of water column.
        
        Position: inside bend - shallow slower-moving water, outside bend - deeper fast-moving water.
      - Methods for measuring velocity:
        
        Flow meter: expensive and unreliable.
        
        Impeller: simple mechanical device.
        
        Mounted on graduated stick and the base on river floor.
        
        Can adjust the height and measure the velocity.
        
        Can only be used in clear shallow water.
        
        Held at the end of side arm and lower into water facing upstream.
        
        Release and take time to travel the distance of side arm.
        
        Float: measure time floating object taking travel in certain distance, reduce wind effect, average flow velocity from surface flow velocity by dividing surface velocity.
- - - - Three cups rotate in the wind
      - number of rotation per time period is counted and converted to a wind speed
      - can be mounted permanently or hand-held
    - - calibriated tube over which wind passes
      - reduce pressure from tube
      - easy to use but expensive
    - - beaufort scale
      - observe the effect of wind on object
  - - - Gravel
        
        coarse and medium
        
        measure individually
        
        simple but time- consuming procedure
        
        fine and very fine
        
        sieved through a series of sieves with different mesh sizes
      - Sand
        
        all size
        
        like the method of fine and very finegravel
      - Silt and clay
        
        sedimentation technique
        
        large particle sink faster than small particle
        
        optical technique
        
        light scattering by particle
        
        automated instrument
        
        expensive for secondary school use
    - - set oven 105 Ceilcius
        
        hot enough to dry soil
        
        preserve organic matter
      - leave for 24 hours and weigh the sample
        
        repeat until mass become stable
      - Organic content
        
        Advantages
        
        Supplies nutrient to soil
        
        Hold water
        
        Reduce compaction and crusting
        
        Increase infilitration
        
        Methodlogy
        
        The loss on ignition (LOI) method
        
        Dry sample
        
        Heat soil at 105 celcius
        
        weigh sample and repeat until mass become stable
        
        Mineral content and pH
        
        Measured through traditional soil testing kit
        
        pH probe
  - - - easy to make
      - there are plenty website for reference
- - - - Quick
      - Accurate
      - Easy to use
    - - Costly
      - Can give false readings without knowing
      - Not available in all countries