Sensing Water Leaks by Their Sound

<...a world suffering water shortages...> TermFail.

The world has about the same amount of water as it ever had. The problem lies only in having sufficient potable water in the right place and in removing the wastewater to the right place.

Correct. Basically you either have people moving to the desert (LA, Las Vegas) and siphoning water from other areas or you've got irrigation creating deserts (Aral Sea), but the water is still around.

Generally easier to detect pressure losses. Also, pressure changes affect sound frequencies, but sinals going through diferent ground densities affect sound, so that may not be the right way to go about it. Generally, a leak is only detected when the sinkhole opens up in the road way, or the wate starts gushing out of the hill. At least in Los Angeles.

Have seen this in use is Aus and it does have some limitations also.

It was suggested to us as a condition monitoring tool for water infrastructure, but cost/km was high (for a 200km pipe set) and could only detect current leaks. It was almost less expensive to replace the pipe than to run diagnostics for pipes each 10 years after 50 years old, especially for reticulationmains.

We have had good results with mounted accousitc devices running a 24 hour time based record and "correlating" the signals.

We have had good results with high gain microphones.

Here is some good information on detecting underground water leaks acoustically:

http://www.subsurfaceleak.com/find_leaks.html