The Pulse-Shunt Hypothesis: Predicting the Evolution of DOM Composition and DOM Subsidies in Drainage Networks

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The transfer of carbon, nutrients, and pollutants from terrestrial environments to streams and the biogeochemical transformations of these constituents within river networks are issues that motivate environmental scientists and water-resource managers. Dissolved organic matter (DOM) is a master variable in streams and rivers that affects contaminant speciation and mobility, light penetration, stream metabolism, pH, and water-treatment efficiency. The goals of this study are to (i) improve approaches for predicting DOM pulses from head-water catchments and (ii) advance understanding of factors that consume and alter DOM during its transit through the downstream drainage network. The project will continue to refine a new model suitable for quantifying DOM transfer from the landscape to streams draining head-water catchments. This model links rainfall-runoff processes that generate stream flow to biogeochemical processes that govern the quantity and composition of terrestrial DOC through changes in catchment-water storage. The model will be tested against measurements of DOM concentration and composition made in several headwater (1st-order) streams of Connecticut's Farmington River Basin. These DOM measurements will also be made in 2nd and 5th-order streams within the Farmington Basin, thereby illuminating the manner in which DOM composition and lability evolve along the drainage network. These observations will be used to test hypotheses for river-network DOM dynamics that are based alternatively on the classical River Continuum concept and a newly proposed Pulse-Shunt concept.This project will provide graduate students and a post-doctoral associate with opportunities to engage meaningfully in lab, field, and quantitative, theoretical research. Equally important, our study will impact the general public by working with the Peabody Museum of Natural History. In particular we will work with New Haven Public high school students to build a "Watershed Teaching Cart" that will be manned by high school students on weekends at the Peabody Museum.