Samenvatting Water 1

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Samenvatting - 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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Laatst toegevoegde flashcards

What is the field capacity?
The wetness of the upper soil layer when the soil has lost iets suplus of water to the groundwater after a wet period.
What is the formula for the storage coefficient?
μ = ΔSw : Δh
 - Δ Sw = rainfall
- Δ h = groundwater change
-  μ = storativity, precentage of air in the soil
Why can clayey soils store less water?
Unsaturated clayey soils normally contain more water in their pores than sandy soils.
What is groundwater storage?
After a rainfall event the groundwater table rises, saturating part of the unsaturated zone.
Hoi :)
What is upward seepage?
Water enters an area via deeper sil layers and subsequently moves upward towards the soil surface.
What is drainage?
Groundwater flowing towards the surface.
What is interflow?
Water cannot percolate to the groundwater because there is a layer with low permeability. I runs parallel to this layer downhill.
What are that causes of water not being able to infiltrate?
1) land surface is impermeable
2) infiltration excess
3) saturation excess
4) seepage
What is capillary rise?
Water is sucked upwards by a negative pressure caused by evatranspiration in the topsoil.