A comparison of residence time calculations using simple compartment models of the Altamaha River estuary, Georgia. Sheldon, J. E. and Alber, M. Estuaries, 2002.
abstract   bibtex   
The residence and flushing times of an estuary are two different concepts that are often confused. Flushing time is the time required for the freshwater inflow to equal the amount originally present in the estuary. It is specific to fresh water (or materials dissolved in it) and represents the transit time through the entire system (e.g. from head of tide to the mouth). Residence time is the average time particles take to escape the estuary. It can be calculated for any type of material (including fresh water), and will vary depending on the starting location of the material. In the literature, the term residence time is often used to refer to the average freshwater transit time and is calculated as such. We explored these two mixing time scales in the context of the Altamaha River Estuary, Georgia, and present a comparison of techniques for their calculation (fraction of fresh water models and variations of box models). Segmented tidal prism models, another common approach, have data requirements similar to other models but can be cumbersome to implement properly. Freshwater transit time estimates from simple steady-state box models were virtually identical to flushing times for four river-flow cases, as long as boxes were scaled appropriately to river flow, and residence time estimates from box models were also in good agreement. Mixing time estimates from box models were incorrect when boxes were improperly scaled. Mixing time scales vary nonlinearly with river flow, so characterizing the range as well as the mean or median is important for a thorough understanding of the potential for within-estuary processing. We are now developing an improved box model that will allow the calculation of a variety of mixing time scales using simulations with daily variable river discharge.
@article{sheldon_comparison_2002,
	title = {A comparison of residence time calculations using simple compartment models of the {Altamaha} {River} estuary, {Georgia}},
	volume = {25},
	abstract = {The residence and flushing times of an estuary are two different concepts that are often confused. Flushing time is the time required for the freshwater inflow to equal the amount originally present in the estuary. It is specific to fresh water (or materials dissolved in it) and represents the transit time through the entire system (e.g. from head of tide to the mouth). Residence time is the average time particles take to escape the estuary. It can be calculated for any type of material (including fresh water), and will vary depending on the starting location of the material. In the literature, the term residence time is often used to refer to the average freshwater transit time and is calculated as such. We explored these two mixing time scales in the context of the Altamaha River Estuary, Georgia, and present a comparison of techniques for their calculation (fraction of fresh water models and variations of box models). Segmented tidal prism models, another common approach, have data requirements similar to other models but can be cumbersome to implement properly. Freshwater transit time estimates from simple steady-state box models were virtually identical to flushing times for four river-flow cases, as long as boxes were scaled appropriately to river flow, and residence time estimates from box models were also in good agreement. Mixing time estimates from box models were incorrect when boxes were improperly scaled. Mixing time scales vary nonlinearly with river flow, so characterizing the range as well as the mean or median is important for a thorough understanding of the potential for within-estuary processing. We are now developing an improved box model that will allow the calculation of a variety of mixing time scales using simulations with daily variable river discharge.},
	number = {6B},
	journal = {Estuaries},
	author = {Sheldon, Joan E. and Alber, Merryl.},
	year = {2002},
	keywords = {GCE, model, discharge, estuary, altamaha, residence time, flow}
}
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