On a global scale, rivers are important processors and conduits of terrestrially derived materials, transporting significant quantities of dissolved and particulate elements to downstream aquatic ecosystems, the atmosphere, and the ocean (Aufdenkampe et al., 2011;Gaillardet et al., 1999;Meybeck, 1982). In particular, the riverine fluxes of carbon (C), nitrogen (N), and phosphorus (P) represent important components of terrestrial net ecosystem production (NEP) and the transfer of energy and nutrients to lotic and marine ecosystems. Major and trace elements in rivers, on the other hand, reflect watershed geology, chemical weathering rates, and hydrology. The concentration, proportions, and fluxes of these elements in rivers represent integrated signals of the various processes that occur throughout the drainage basin, including mobilization, dilution, transport, transient storage, and weathering (Wohl, 2020). Time series datasets of concentration and water discharge allow for further refinement of annual flux estimates and can indicate the degree to which a given constituent is mobilized, diluted, or responds chemostatically with respect to discharge (Godsey et al., 2009;House & Warwick, 1998). Moreover, the geochemistry of rivers can be used to estimate the rate of continental denudation and the related consumption of atmospheric CO 2 , one of the major goals of river geochemistry (Gaillardet et al., 1999).