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Ground‐Water Discharge to Lakes: Focusing in Embayments
Author(s) -
Cherkauer Douglas S.,
McKereghan Peter F.
Publication year - 1991
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.1745-6584.1991.tb00499.x
Subject(s) - bay , shore , groundwater recharge , geology , aquifer , hydrology (agriculture) , groundwater , equipotential , geomorphology , oceanography , geotechnical engineering , geography , cartography
Abstract Seepage of ground water to Green Bay and Lake Michigan from a fractured dolomite aquifer beneath the Door Peninsula of Wisconsin is examined to determine the influences of embayments on the relative amounts of ground‐water discharge. A digital simulation has been used to calculate the quantity and distribution of that discharge. The simulated results are based on the net recharge which occurs on the land portion of the study area. They compare favorably with discharges calculated by flow net using observed hydraulic gradients and conductivities, and are in relative agreement with direct measurements made by seepage meters. The simulation has not been verified (due to lack of independent observations), but the similarity of the discharges from the three methods is argued to indicate the model's validity. In the study area, 66,000 m 3 /day of ground water is discharged directly to Green Bay (26,000 m3/day) and Lake Michigan (40,000 m3/day). Almost 60% of this total occurs in 20 embayments along the shore, even though they occupy only about 33% of the shoreline length as measured parallel to the long axis of the peninsula. Discharge is focused into embayments by distortion of equipotential lines caused by a bay's penetration into the ground‐water system. In the study area, it is shown that flow amplifications of up to 500% vary directly with two measures of the shoreline shape at bays, horizontal penetration (defined as the ratio of a bay's axial length to the distance to the ground‐water divide), and vertical penetration (the ratio of the maximum bay depth to aquifer thickness). Both factors have equal influence on the amplification of discharge. A graphical means of predicting the effect of coastal configuration on other bays is presented, but its applicability outside the study area is unknown.