“…In search for methods to overcome this data gap, the PUB initiative helped to raise interest in the development of innovative in situ gauging techniques, as well as the use of remotely sensed earth observation data. Nowadays, precipitation (TRMM, Kummerow et al, 1998;GPM, Hou et al, 2014), evaporation and water stress (Bastiaanssen et al, 1998;van Emmerik et al, 2015), topography (DEM), large scale groundwater variation (GRACE, Mulder et al, 2015), reservoir dynamics (Eilander et al, 2014) and soil moisture (SMOS, Kerr et al, 2001;SMAP, Entekhabi et al, 2010; AMSR-E, Khan et al, 2012), among others, can be estimated on a global scale, with high temporal and spatial resolution. However, in most PUB cases these data are only used as model inputs, while hydrologists still rely on discharge measurements as a calibration and validation tool.…”