“…In addition to these box approaches, a number of more comprehensive mechanistic models, describing biogeochemical processes involved in carbon cycling and CO 2 evasion, have been set up for oceans (e.g., Doney et al, 2004;Aumont et al, 2015), coastal waters (e.g., Borges et al, 2006;Gypens et al, 2004Gypens et al, , 2009Gypens et al, , 2011 and estuaries (e.g., Cai and Wang, 1998;Volta et al, 2014;Laruelle et al, 2019). In inland waters, the NICE-BGC model (Nakayama, 2016) accurately represents CO 2 evasion at the global scale. However, to our knowledge, while several process-based river models describe the carbon cycle through organic matter input and degradation by aquatic microorganisms (e.g., PEGASE, Smitz et al, 1997;ProSe, Vilmin et al, 2018;QUAL2Kw, Pelletier et al, 2006;QUAL-NET, Minaudo et al, 2018, QUASAR, Whitehead et al, 1997Riverstrahler, Billen et al, 1994;Garnier et al, 2002), none of them describes the inorganic carbon cycle including carbon dioxide outgassing.…”