Gravity monitoring has been reported from at least 26 geothermal sites around the world, successfully measuring the water recharge and sustainability of the process.
Quad Geometrics

In geothermal reservoirs, Hot water is extracted from the subsurface and the aquifer may be re-charged naturally with lateral flow, or cold water injection may take place.

Gravity monitoring of geothermal reservoirs has helped determine the natural and injected water inflow distribution and phase since the 1960s, with pioneering work in New Zealand (Allis and Hunt, 1986; Hunt and Kissling, 1994), Japan (Sugihara and Ishido, 2008), Philippines (Nordquist et al., 2004), and Indonesia (Sofyan, 2011).