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Tidal Load and Salt Water Influences on Submarine Ground Water Discharge
Author(s) -
Paulsen Ronald J.,
O'Rourke Daniel,
Smith Christopher F.,
Wong TengFong
Publication year - 2004
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/j.1745-6584.2004.tb02638.x
Subject(s) - geology , submarine groundwater discharge , aquifer , groundwater , bay , hydraulic head , hydraulic conductivity , hydrology (agriculture) , lag , submarine , environmental science , geotechnical engineering , oceanography , soil science , soil water , computer network , computer science
Field measurements were conducted to characterize the influences of salt water and tidal loading on submarine ground water discharge (SGD) into West Neck Bay on Shelter Island, New York. SGD was continuously recorded at three sites using an ultrasonic ground water seepage meter, and the spatial extents of the terrestrially derived SGD and the salt water/fresh water mixing zone were inferred from electrical conductivity profiling. While SGD increases with increasing hydraulic gradient in the far field of the coastal aquifer, shorter temporal variations of SGD were inversely correlated with tidal stage. SGD and hydraulic heads in the onshore unconfined aquifer near the coast responded asymmetrically to tidal loading, with discharge and head increasing faster than decreasing. A time lag of ∼1 h was observed between the tidal load and responses in onshore head and SGD. This lag represents a manifestation of the travel time required for tidal influences to propagate landward before the hydraulic gradient adjusts and influences seepage. The spatial extent of the fresh water component of SGD determined by electrical conductivity profiles, seepage velocity, and the time lag between tide and SGD amplitudes are in reasonable agreement with analytic estimates.