“…Using retracked river observations, inland radar altimetry can accurately measure changing river surface elevation (Koblinsky et al, 1993;Berry et al, 2005;Frappart et al, 2006;Alsdorf et al, 2007;Santos da Silva et al, 2010;Papa et al, 2010;Dubey et al, 2015;Tourian et al, 2016;Verron et al, 2018). While custom retrackers have been derived and tested in particular locations (Huang et al, 2018;Maillard et al, 2015;Sulistioadi et al, 2015) the ICE-1 retracker (Wingham et al, 1986) is arguably the best compromise between being consistently reliable and available for many altimeter missions (Biancamaria et al, 2017;Frappart et al, 2006;Santos da Silva et al, 2010). While available globally, the ICE-1 retracked data must be extracted over river targets, and carefully filtered, to make them useful to global hydrological modeling applications.…”