Residence time

[Sara]

I'm using the database for some kind of statistical studies. I wonder how the residence time has been calculated in the "Effects of nutrient enrichment in the nation's estuaries: A decade of change". I extracted the residence times from the appendices at the end of the report. I tried to get the residence time from the "estuary volume(m^3)/daily fresh water(m^3/d)" but I don't get any result close enough to those in the article. Can you please help me in this matter? Thank you.

[suzanne]

Hi Sara,
Thanks for your inquiry. I'd like to know what you're working on.
This is an issue that has created a lot of angst over the years since there isn't a good way to estimate residence time the same way for all the systems because of their differences in, for example, freshwater inflow. During the course of the NEEA we tried to make calculations the same way for all systems for consistency but this created problems when we wanted to address residence time. I spent a lot of time trying to figure out the dividing place between when the freshwater inflow model should be used and when a tidal prism model would be more appropriate. I couldn't find any pattern and so to be consistent we used the freshwater inflow model for all of them, knowing that we could do better but not being able to spend the time to do so. We thought it would make a really great MS thesis for someone. Anyway, we ended up using a salinity based, basically freshwater inflow model that also balanced evap and ppt for all of them. There are a few systems (i.e. MD inland bays) that we used the residence times that the NEEA participants determined and sent to us.
If you want, I can send you the xls with the pertinent data so you can see what we did. Let me know.
I hope these comments are helpful.
Suzanne

[Sara]

Actually I'm trying to find the most effective parameters on the eutrophication condition of an estuary,and I'm doing some statistical studies and plots by using the NEEA database (residence time from the NEEA report_2004).

I calculated the residence time in 2 ways:

1)  Residence time= estuary volume /freshwater inflow

2)  Residence time= (estuary volume /freshwater inflow)*((S ocean - S estuary) /S ocean)     
            S ocean: Salinity in coastal ocean,which I assumed to be 35 for all estuaries
            S estuary: Salinity of the estuary ,Average Salinity (psu) from the database

but from both ways I got significant differences. In some estuaries the ratio of RT I got is 10 times larger than those in the report.
I'd really appreciate it if you can send me those excel files.
Thank you for your time and consideration.

[suzanne]

Hi Sara,

Could you send me your email address? I'd prefer not to post the file here.

Thanks,
Suzanne

[Sara]

Dear Suzanne,
 
here is my email address: sxg3832@louisiana.edu

Thank you
Sara