A method for estimating pore water drainage from marsh soils using rainfall and well records
A method for estimating pore water drainage from marsh soils using rainfall and well records
Date
2008-03-05
Authors
Gardner, Leonard Robert
Gaines, Emily F.
Gaines, Emily F.
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Abstract
Rainfall events during low tide exposure cause the water table in marshes to rise.
If one has long time series of both rain events and water levels in wells along transects
from creek bank to marsh interior, one can correlate well response with rain amount. In
cases examined so far the well response is found to be a linear function of rain amount.
As it is reasonable to assume that the amount of tidal infiltration required to restore the
water table to the elevation of the marsh surface is equal to the amount of rain that would
be required to do so, one can estimate the annual drainage of pore water from a well site
by dividing the mean drawdown of the water table at low tide by the slope of the
response-versus-rain regression and then multiplying the result by the number of tidal
drawdowns in a year. Integration of such results along the transect then gives an estimate
of the total annual drainage. An example of the use of this method is given for two well
transects in a Typha and a Spartina marsh at the Plum Island Estuary Long Term
Ecological Research (PIE-LTER) site in Massachusetts, USA. Both transects yielded
pore water drainage rates of about 160 m3 yr-1 per meter of channel length. Although the
annual volume of pore water drainage is small compared to the annual volume of the tidal
prism its impact on nutrient budgets in the estuary could be large because of the high
concentrations of nutrients in marsh pore waters. We also discuss the possible effects of
the capillary fringe, air entrapment and tidal forcing during rain events on these results.
Description
Author Posting. © The Author(s), 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Estuarine, Coastal and Shelf Science 79 (2008): 51-58, doi:10.1016/j.ecss.2008.03.014.