Does Lunar Gravity Affect Lake Water Levels?

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Discussion Overview

The discussion centers on whether the gravitational pull of the moon affects water levels in enclosed lakes, exploring the implications of lunar gravity on lake water levels and comparing it to ocean tides.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • Some participants propose that the moon's gravitational pull does affect water levels in enclosed lakes, albeit to a very small extent.
  • Others argue that the change in elevation due to lunar tides is proportional to the average depth of the water, leading to minimal effects in most lakes.
  • A participant explains that the large amplitude of ocean tides is influenced by the interaction of tidal waves with shallow depths and the shapes of sea areas, which do not apply to most lakes.
  • It is suggested that the magnitude of solar and lunar tides in lakes would be on the order of a few millimeters at most.

Areas of Agreement / Disagreement

Participants express differing views on the extent to which lunar gravity affects lake water levels, with no consensus reached on the significance of this effect.

Contextual Notes

Limitations include the dependence on definitions of "enclosed lakes" and the assumptions regarding the average depth of water in these lakes.

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Does the grav pull of the moon affect the water level in enclosed lakes?
 
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rc1102 said:
Does the grav pull of the moon affect the water level in enclosed lakes?

Yes it does, but since the change in elevation due to the tides is (approximately) proportional to the average depth of the water, it is very small for most lakes.
 
The relatively large amplitude of ocean tides around coastlines is caused by two effects.

1. The interaction of the long-period "tidal wave" with the shallow depth (which is exactly the same as for wind-driven waves, except orders of magnitude slower). This is the main cause of the high tidal range in shallow estuaries.

2. The particular shapes of sea areas (e.g the varying width of the Atlantic and Pacific oceans with latitude) allow standing waves to form with periods close to the main tidal excitiation frequencies. This can cause large variations in the amplitudes of tidal compoents with periods close to 12 and 24 hours. (The idea that "the moon causes two tides per day" is a gross oversimplification of actually happens in many parts of the world).

Most lakes are much too small for either of these effects to be significant, and the magnitude of solar and lunar tides would be of the order of a few mm at most.
 
Thank guys, was just to settle an arguement
 

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