ESA Climate Change Initiative River Discharge Precursor (RD_cci+) D.3 River Discharge (RD) from altimeters, river- width, multispectral images and data combination Algorithm Theoretical Basis Document (ATBD) Contract number: 4000139952/22/I-NB Reference: RD_CCI-0006-ATBD Issue 2.0 31/07/2025 Tel +33 (0)5 61 39 11 rue Hermиs, Parc Technologique du Canal — 31520 Ramonville Saint-Agne, France Tel +33 (0)5 61 39 47 00 Fax +33(0)5 61 75 10 14 www.cls.fr