# Goswami PG 587

environmental water resources

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### #1 MrAnderson

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Posted 21 October 2011 - 09:33 PM

Hi Guys,

So I was running through the NCEES practice problems and one of them asked to use the "critical oxygen deficit" equation for the Streeter-Phelps Dissolved oxygen sag curve. I was using Goswami's equation:

tc = (1/kr-kd) x ln[(kdLo-krDo+kdDo)/kdLo) x (kr/kd)].

I ended up getting the wrong answer, as it turns out (from the solution, google, and other sources) the equation they used was:

tc = (1/kr-kd) x ln[(1-(Do(kr-kd)/kdLo) x (kr/kd)]

This is very frustrating, there are so many little mistakes in the Goswami book that I find myself wasting my time cross checking it's validity. Which equation should I use when it comes time for the exam?

Edited by MrAnderson, 21 October 2011 - 09:33 PM.

### #2 civilized_naah

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Posted 22 October 2011 - 03:01 AM

How are those 2 equations different?

### #3 civilized_naah

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Posted 23 October 2011 - 04:36 PM

MrAnderson,
I would really like to know which one of those equations is the correct one. I can't spot the difference!

### #4 thebettersmith

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Posted 24 October 2011 - 04:16 PM

Mr Anderson.. the 2nd equation simply factors the 1st equation, sir.

Mr. Smith

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