Fluxes to estuarine and coastal environments
|West Falmouth Harbor and study sites from 2010|
|Model grid of West Falmouth Harbor with groundwater inputs|
Buzzards Bay and West Falmouth Harbor are estuarine embayments on the western edge of Cape Cod. The input of freshwater on the eastern margin of Buzzards Bay adjacent to Cape Cod and West Falmouth Harbor is largely due to groundwater. In West Falmouth Harbor, the groundwater that seeps into the harbor is characterized by high levels of nitrate, up to 250 uM. This high nitrate load has modified the ecology of the harbor and may be a significant source of nitrate to Buzzards Bay during seasons with low biological nitrate uptake. The U.S. Geological Survey undertook measurements in West Falmouth Harbor to improve understanding of circulation, residence time, and water quality in the harbor and bay. We set up and monitored multiple sites in both Buzzards Bay and West Falmouth Harbor, measuring depth, water velocity,salinity, pH, dissolved oxygen, chlorophyll-a, and nitrate concentration.
The complete time-series from multiple sites in Buzzards Bay and West Falmouth Harbor is presented by Ganju et al. (2011). Ganju (2011) used these data to compute the flux of freshwater into a tidal creek at the landward end of the Harbor, using a new method that combines the index-velocity method with a salt-balance calculation (Total Exchange Flow). The methods were then applied at the mouth of the Harbor to estimate the total groundwater flux to the Harbor (Ganju et al., 2012). These data provide a new way to estimate nutrient loading to groundwater-fed, microtidal estuaries. Access to the data is here.
Ganju, N.K., Dickhudt, P.J., Thomas, J.A., Borden, J., Sherwood, C.R., Montgomery, E.T., Twomey, E.R., and Martini, M.A., 2011, Summary of oceanographic and water-quality measurements in West Falmouth Harbor and Buzzards Bay, Massachusetts, 2009-2010, USGS Open-File Report 2011-1113. Link to report
Ganju, N.K., 2011, A novel approach for direct estimation of fresh groundwater discharge to an estuary, Geophysical Research Letters, 38, L11402, doi:10.1029/2011GL047718. PDF File
Ganju, N. K., Hayn, M., Chen, S. N., Howarth, R. W., Dickhudt, P. J., Aretxabaleta, A. L., and Marino, R., 2012, Tidal and groundwater fluxes to a shallow, microtidal estuary: constraining inputs through field observations and hydrodynamic modeling, Estuaries and Coasts, 35, 1285-1298. PDF File