Jd. Hagy et al., Estimation of net physical transport and hydraulic residence times for a coastal plain estuary using box models, ESTUARIES, 23(3), 2000, pp. 328-340
A box model based on salinity distributions and freshwater inflow measureme
nts was developed and used to estimate net non-tidal physical circulation a
nd hydraulic residence times for Patuxent River estuary, Maryland, a tribut
ary estuary of Chesapeake Bay. The box model relaxes the usual assumption t
hat salinity is at steady-state, an important improvement over previous box
model studies, yet it remains simple enough to have broad appeal. Average
monthly 2-dimensional net non-tidal circulation and residence times for 198
6-1995 are estimated and related to river flow and salt water inflow as est
imated by the box model. An important result is that advective exchange at
the estuary mouth was not correlated with Patuxent River flow, most likely
due to effects of offshore salinity changes in Chesapeake Bay. The median r
esidence time for freshwater entering at the head of the estuary was 68 d a
nd decreased hyperbolically with increasing river flow to 30 d during high
flow. Estimates of residence times for down-estuary points of origin showed
that, from the head of the estuary to its mouth, control of flushing chang
ed from primarily river flow to other factors regulating the intensity of g
ravitational circulation.