In this study, we present the concentration vs discharge relationships of total suspended solids (TSS), total dissolved solids (TDS), particulate organic carbon (POC) and dissolved organic carbon (DOC) in the tributaries and main-stems of two small mountainous river systems in northern California and central Oregon (Eel and Umpqua River systems, respectively), USA. In order to determine total suspended solids (TSS) concentrations, known volumes of water (100-500 ml) were vacuum-filtered onto pre-combusted (450 oC for 3 hours), pre-weighted 47 mm diameter, GF/F filters (0.7 um nominal pore size). Once filtered, samples were kept frozen inside individually labeled petri dishes until they were oven dried (60 oC for 24 hour). Following the drying step, filters were weighed and the mass of TSS calculated by subtracting the weight of the filter. TSS concentrations (g m-3) were calculated by dividing the mass of TSS by the volume filtered. Total dissolved solids (TDS) concentrations were determined by filtering known volumes of water (~250 ml) through 0.8 um cellule filters to remove particulate materials. Concentrations of anions (Cl-, NO3-, PO43-, F- and SO42-) were determined using a Dionex 1500 Ion Chromatograph using the US EPA Method 9056A at the Cooperative Chemical Analytical Laboratory at Oregon State University. Major cations were measured with a Spectros Arcos ICP-OES in axial mode at the Keck Collaboratory at Oregon State University. Dissolved cations analyzed include Al, B, Ba, Ca, Fe, K, Li, Na, Mg, S, Si, and Sr. TCO2 and pCO2 analyses were made following methods described in Bandstra et al. (2006), and these two parameters were then used to solve for the other carbonate system parameters, including HCO3. TDS concentrations (g m-3) in this study are calculated as TDS=HCO3+SiO2+SO4*+Na*+Mg*+Ca*+K*+2xDOC, where * indicates concentrations corrected for atmospheric inputs and DOC indicates dissolved organic carbon concentrations. Particulate organic carbon (POC) concentrations were determined by filtering known volumes (50 to 100 ml) of water through 13-mm diameter GF/F filters (0.7 um nominal pore size). Once filtered, samples were exposed to concentrated HCl acid fumes to remove carbonates and then analyzed by high temperature combustion according to established procedures (e.g., Goñi et al., 2013). POC concentrations (g m-3) were calculated by dividing the mass of carbon and nitrogen by the volume filtered. In the case of dissolved organic carbon (DOC), water samples were filtered through 0.45 um pore-sized acro-discs immediately after collection, into pre-acidified amber glass vials. We measured DOC concentrations (g m-3) by high temperature oxidation using a Shimadzu TOC-VSCH analyzer at the Oregon State University’s Institute for Water and Watersheds Collaboratory.