Simulating streamflow and dissolved organic matter export from a forested watershed

Abstract

Stream water concentrations of dissolved organic matter (DOM) exhibit large temporal variations during precipitation on forested, headwater catchments. We present a modeling framework appropriate for describing streamflow and event‐driven export of DOM from small, forested watersheds. Our model links parametrically simple formulations for rainfall‐runoff generation and soil water carbon dynamics. The rainfall‐runoff formulation is developed by modifying the catchment model of Kirchner (2009) to account for hysteresis in the relationship between stream discharge and catchment water storage. Time series computations of catchment water storage are used by the soil carbon model to approximate the effects of leaching, adsorption, and mineralization on soil water DOM concentrations and the export of DOM from the terrestrial reservoir to the stream. Our findings show that this model is capable of reproducing hourly variations of stream discharge (ranging from 0.01 to 0.38 mm h−1) and stream water DOM concentrations (ranging from 1.8 to 14 mg C L−1) measured in a forested headwater stream in north central Massachusetts. Our analysis highlights the strong linkage between soil carbon dynamics and hydrological processes that govern catchment water storage and flow paths connecting the terrestrial system to the stream.