If we are not living sustainably, should we expect more investment across the world on things like desalination plants (I understand that desalination is really energy-expensive currently, but will that change by much?)
The conclusion is: Probably the most at-risk aquifer (based on people affected and severity) is in the Gangetic plain in northern India. There are also critically threatened aquifers in the Arabian peninsula, southeast China, and our own Sacramento Valley.
This conclusion is supported by other hydrological modeling groups as well (e.g., the very highly-cited, but older, http://onlinelibrary.wiley.com/doi/10.1029/2010GL044571/full)
However, long term it's a finite resource. At the same time a lot of fresh water ends up in the ocean so desalination needs to compete with simply moving water around.
Locally when transport is more expensive than desalination it may be useful, but long term it's a balancing act between moving water a thousand miles+, desalinating locally, or increasing efficiency.
PS: In theory these Aquifers could be used as a cheap form of transport, but when any well get's to tap the water for 'free' who pays for it becomes a major issue.
For what it's worth, an aquifer isn't an underground river... It's solid rock. What would you be transporting?
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There's far more fresh water falling on the US than is being "used". Go look at any river. Gazillions of litres of fresh water per minute just flowing out to sea and getting salty. Then imagine the number of rivers doing that.
Of course damming every river and diverting it to other uses is impractical and would have bad effects on various ecosystems, but there's a lot of spare fresh water just running out to sea.
And then remember that the vast majority of the water that we "use" is not getting split into hydrogen and oxygen, it's staying molecular water and it's hanging around.
Saying we have far more than is being used is true, but misses the forest for the trees. Some areas have lots of water resources, some don't.
Unfortunately our water usage is almost inversely correlated to water resource availability. Arid soils are _incredibly_ productive when irrigated, so we grow a lot of crops in the desert (or semi-desert). Also, people like to live in dry, sunny places. Dry, sunny places usually don't have abundant water resources.