Importance of water movement

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Water Movement

• Importance of water movement
• Arrhythmic water movements
• Rhythmic water movements

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Importance of Water Movements

• Erosion and deposition
• Distributes heat
• Distributes dissolved substances
• Distributes organisms

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Types of Arrhythmic Water Movements

• Currents
• Influent and effluent currents
• density plumes (salt, turbidity, temperature)

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Turbidity Plume
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• Currents generated by the wind
• surface currents
• upwelling and downwelling
• Langmuir Spirals

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Langmuir Spirals
Figure 5-13 in Horne Goldman
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• Inertial Effects
• Coriolis Effect
• Ekman Spirals

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• Turbulence and Eddy Diffusion
• Importance
• Distributes heat
• Distributes nutrients
• Transports plankton
• Molecular diffusion

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• Characteristics
• laminar flow no intense mixing phenomena
• turbulent flow mixing throughout the flow field

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• Important Dimensionless Numbers
• Reynolds Number distinguishes between laminar
  and turbulent flow
• Richardson Number the ratio of buoyancy to
  mixing
• Wedderburn Number reflects the stability of the
  seasonal thermocline
• Details will be covered in section.

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Types of Rhythmic Water Movements

• Capillary waves ripples where surface tension
  is a restoring force

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• Gravity waves
• Deepwater waves
• depth to bottom, d gt ½ ?
• Transitional waves
• ? lt d lt ½ ?
• Shallow water waves
• d lt ? ? wave can feel the bottom

?
d
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• Gravity Wave Propagation Characteristics
• Increasingly elliptical paths with shallow depths
• Motion dampened with depth
• amplitude (A) of motion at a given depth (z)

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• Seiches, i.e. standing waves
• very long waves, d lt ½ ?
• causes much greater water displacement than
  traveling waves

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Seiches can have very complex patterns

• Types of Seiches
• longitudinal
• transverse
• unimodal
• bimodal

• dicrotic
• plurinodal
• external
• internal

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• Seiches initiated by
• accumulation of water due to wind action
• sudden local changes in water level due to heavy
  rainfall, local inflow
• sudden local changes in barometric pressure
• landslides
• earthquakes

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• Seiche Period duration of the to and fro
  movement in a unimodal oscillation
• for a unimodal seiche in a rectangular basin
• where t period
• L length of basin
• g acceleration due to gravity
• d depth of water

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Key Points

• Water movements are important because it
• mixes dissolved and suspended material
• distributes heat and moves organisms
• causes erosion and deposition
• Water movement can be arrhythmic or rhythmic