Summary Water 1

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Summary - Water 1

  • 1 Catchments

  • Hoi :)
  • 1.1 Catchment characteristics

  • What is a catchment and why is this unit used?
    The area from which excess water flows towards that river.
  • Which landscape properties affect hydrology?
    1) size
    2) typography
    3) landcover
    4) geology
  • How can the catchment boudary be delineated?
    1) Topographical water divide (follows the highest point in the landscape)
    2) Groundwater devide (infiltrating water may hit an impermeable layer in the ground and be led in another direction
  • What is the 1st zone of a catchment?
    Zone 1 : Upper course / upstream area / production zone
    - dense dendritic network of channels 
    - surface water and sediments are formed
  • What is the 2nd zone of a catchment?
    Zone 2 : Middle course / transport zone
    - main channel which meanders throug the landscape
    - surface water and sediments are transported
  • What is the 3d zone of a catchment?
    Zone 3 : Lower course / downstream area / deposition zone
    - multiple braches as a result of the flat landscape
    - low flow velocity causes sediment to settle
  • What is the topographic wetness index
    Draining area : local slope
    High is wet
  • Which hillslopes are the wettest?
    Concave converging slopes
  • Which hillslopes are the dryest?
    Convex diverging slopes.
  • What is porosity?
    The fraction of open spaces between the soil particles. Detirmines how much water is stored underground.
  • What is conductivity?
    A measure of how easy it is for water to flow betweeen soil particles. Determines how quickly water is transported.
  • What is an aquifer?
    A layer of permeable soil. Can store and transport water well.
  • What is a DEM?
    Gives the elevation for each pixel on a map.
  • What is a GIS?
    This spatial data can be used as input for computer models simulating the hydrological processes in different parts of the catchment en predict river discharge.
  • 1.2 Channels

  • What is topology?
    Channel networks.
  • What is the formula for drainage density?
    Dd = Ltot : A
    Dd = drainage density
    Ltot = total length of the channels
    A = certain area (m2)
  • What does an high drainage density indicate?
    A certain area contains many channels and the average distance from a location on land to the nearest channel is small. And there is water flowing on the ground (low conductivity, farming)
  • What is a dendritic pattern?
    Tree shaped channel network. Homogeneous geological fromations.
  • What is a radial pattern?
    Streams start from 1 central point and flow into all directions.
  • What is a trellis pattern?
    Large number of cahnnels that have the same direction on easch side of the river. Folds in the earths crust.
  • What is a parallel pattern?
    Occurs on steep slopes where the water flows downhill fast.
  • What are the rules of Strahler order numbering?
    - exterior links get order 1 (links between source and first junction)
    - when links of the first order merge, add 1
    - when links with different orders merge, it will continue as the highest
    - the highest order is always found at the outlet and represents the Strrahles order of the catchment
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What is the opposite of bottom-up control?
Trophic cascade
What is the aquatic food web?
1st level: phytoplankton
2nd: zooplankton
3rd: planktivorous fish
4th:piscivorous fish
What are the forms of biological interaction?
1. competition
 - scramble competition
-interference competition
2. Predation  
-food web relations
Which 3 aspects determine the structure and fuctioning of a biological community?
-substance and energy cycle
- competition
- food web
How can streams and rivers be restored?
1. Take away source: water quality (( reduce loading and disccharge of waste water)
2. Water management: reduce peak discharges to prevent weirs
3. Natural morphology
4. Measures
- re-meandering (restore natural profile)
- remove obstacles -> install fish ladders
- retention areas, inundation zones
What are threats to streams and rivers?
-water quality (discharge of waste water)
-regulation of morphology (meanders weghalen etc)
- obstacles (weirs/stuwen)
-dams and reservoirs
Where do functional groups of macro-invertebrates live in the RCC?
Predators: spread throughout whole river
shredders: predominantly upper reach and a little in middle reach
grazers: middle reach and a little in upper reach
collectors: predominantly lower reach
What are the functional groups of macro-invertebrates?
- shredders: CPROM > 1mm
-collectors: filter/collect FPROM 0,5 mum-1 mm
-scrapers/grazers: eat periphyton
What are the characteristics of the middle reach of streams and river, compared to the upper reach?
- less input organic matter
- more open: aquatic plants
- lower flow velocity
- high primary productivity
What are the characteristics of the lower reach of streams and rivers?
- minimal input organic matter
- phytoplankton-dominated
-low flow velocity
-primary productivity