We have developed and tested a 3D Surface Nuclear Magnetic Resonance imaging method (3D-SNMR), which is a new non-invasive geophysical tool for investigating 3D water distribution in the subsurface. Between 2009 and 2011 this method was successfully applied to investigation of a glacier body. In the Tête Rousse glacier (Mont Blanc area in French Alps), we have detected a large cavern containing about 50000 m3 of water, representing potential danger for local population. Basing on our results water was pumped out. After the pumping, we carried out a one-year monitoring of the glacier. Results show that after being drained the cavern was fully refilled again in one year but its volume diminished about three folds. All 3D-SNMR results were found in a good agreement with boreholes and pumping results. At our knowledge it was the first time when the 3D-SNMR was used for investigating glaciers.