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Where in the Marsh is the Water (and When)?: Measuring and modeling salt marsh hydrology for ecological and biogeochemical applications
Citation:
Marois, D. AND J. Stecher. Where in the Marsh is the Water (and When)?: Measuring and modeling salt marsh hydrology for ecological and biogeochemical applications. Hatfield Marine Science Center Seminar Series, Newport, Oregon, May 03, 2018.
Impact/Purpose:
This research was conducted to improve the understanding of salt marsh hydrology by intensely measuring it at several sites and developing a dynamic model using the resulting data. This work fulfills a need in the scientific modeling community for a simple way to simulate salt marsh hydrology so that other processes dependent on hydrology may be accurately predicted. We found that it was possible to develop a simple, low parameter model that can predict salt marsh inundation and inform other modeling efforts. This is relevant to protecting the environment because salt marshes rely on their unique hydrology to provide important ecosystem services to their surrounding communities and environments. Models allow us to predict how these services may vary with environmental changes, which can provide insight into what we can expect to happen to them in various potential future scenarios.
Description:
Salt marsh hydrology presents many difficulties from a measurement and modeling standpoint: the bi-directional flows of tidal waters, variable water densities due to mixing of fresh and salt water, significant influences from vegetation, and complex stream morphologies. Because of these difficulties, there is still much progress to be made in the development of a truly mechanistic model of salt marsh groundwater and surface-water hydrology. This in turn creates an obstacle for simulating other marsh processes, such as nutrient cycling, that rely heavily on hydrology as a biogeochemical control and as a mode of nutrient transport. As a solution, we have used a wealth of collected marsh water level data to create a simplified, hourly time-step marsh hydrology model with few parameters in the dynamic modeling software Simile. The model predicts the response of marsh groundwater level to tides and precipitation as a function of elevation, soil characteristics, and distance from tidal channel. Validation was conducted using well data from a separate transect in Winant Slough and from mesotidal marshes in Tillamook Bay, Oregon. Model outputs can predict how long an area of the marsh will be inundated given a precipitation event or high tide level. This enables scenarios of changing sea level, precipitation, and marsh surface accretion/erosion rates to be tested for their effects on surface and ground-water hydrology, which can inform further effects on vegetation, biogeochemistry, material transport, and habitat value.