Actually - not sure there is ...

Actually - not sure there is much "emerging" right now.  Most of the available technologies for leak detection have existed for some years - what is "emerging" is that water utilities are finally getting around to using them.   A rule of thumb classification:

- acoustic detection - leaks have acoustic signatures in pipes and may also cause pressure transients if large and sudden enough;

- "virtual sensing" - comparing flows and pressures (and sometimes pump energy consumption), both over time and through comparison with a hydraulic model, to detect anomalies against expected levels;

- crowdsourcing - getting the public to report damp spots in the street;

- leak and burst risk assessment and prediction, based on background factors such as soil type, pipe age and type, traffic levels near the pipe, construction activity, pipe usage history and so on;

- in-pipe inspections.

These approaches are not mutually exclusive.

Most recently, the addition of artificial intelligence (AI) to many of these techniques has been getting attention, although in reality machine learning (a form of AI) has been used for some years.   What has held back the widespread adoption until now has been more mundane factors like the value of water not justifying the cost of fixing the leak; lack of system instrumentation; and in many places, lack of suitable subdivisions of the water system (eg DMAs) to allow the leak detection task to be systematically broken down area by area.

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