[jcattle]

Just a fun interjection from my side: The best way we have at the moment to systematically measure groundwater reserves (and depletion) is via proxy of gravity measurements.

The only thing on earth which is heavy and mobile on short time-scales is water. We can measure gravity so exactly that we can measure this movement of water by measuring gravity.

[mjhay]

It’s also probably the best single method of inferring ice sheet mass balance over wide areas.

[RupertSalt]

Does the influence of the Moon make this a three-body problem?