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Development of an ecohydrological salt marsh model
Citation:
Stecher, J., Bob Mckane, A. Brookes, Ted DeWitt, C. Brown, AND Jim Kaldy. Development of an ecohydrological salt marsh model. Presented at CERF 2013, San Diego, CA, November 03 - 07, 2013.
Impact/Purpose:
Terrestrial nitrogen input to coastal waters is a critical water quality problem nationwide. This contribution presents the extension of a successful terrestrial ecohydrological model to assess the ability of a tidal wetland system to mitigate nitrogen runoff. The extension developed and tested herein will be applicable to a broad variety of coastal wetland systems nationwide.
Description:
Terrestrial nitrogen input to coastal waters is a critical water quality problem nationwide. Even in systems well described experimentally, a clear understanding of process-level hydrological and biogeochemical controls can be difficult to ascertain from data alone. For example, an empirical mass-balance approach to characterize the nitrogen flux between a small, meso-haline salt marsh and its estuary in central Oregon yielded an extensive set of flow and water chemistry data, but a significant population of the nitrogen fixer Alnus rubra (red alder) in the upland catchment led to large, highly variable, and diffuse nitrate inputs. This, along with difficulties balancing the water budget, led to large uncertainties in the nitrogen budget. Accordingly, we used these data as a foundation for a more detailed analysis using a process-based model. We augmented the existing terrestrial ecohydrological model, VELMA, which has been used to simulate effects of climate and land use on daily carbon, nitrogen and water dynamics in forested and agricultural watersheds, with a tidal wetland submodel using a sub-daily time step. This extension was undertaken to estimate more accurately (1) terrestrial and estuarine inputs of water, carbon and nitrogen to the marsh, and (2) process-level hydrological and biogeochemical interactions controlling net nitrogen fluxes between marsh and estuary. Here, we will present the structure of the model, its parameterization for a small salt marsh on the Yaquina estuary (Oregon, USA), and preliminary results simulating the exchange of water and nutrients between the uplands, marsh, and adjacent estuary.