Hydrologic events and watershed biogeochemistry: The Pulse Shunt Hypothesis

Abstract:

Pioneering stream tracer releases documented the importance of small streams as hotspots for biogeochemical reactions. Results from these experiments were used in modeling studies to demonstrate the importance of reactions in small streams to mass fluxes of nutrients in large watersheds. Numerous studies, however, using different mathematical approaches have recently argued for a greater importance of larger rivers. We have developed a new conceptual concept called the Pulse-Shunt Concept, which uses drainage network geomorphology, discharge event statistics and hydraulic equations to test the relative importance of small streams versus rivers for the mass transport of dissolved organic matter to the coast in a representative 8^th order New England watershed. We conclude that large systems are the site of the majority of reactions and also explore scaling relationships in drainage network biogeochemistry.