Dissolved Oxygen

[wschinke]

Hey guys:

does anyone understand why DO levels fluctuate so much in a single day, especially this early in the season? Once there is more vegetation later on in the season it would seem more reasonable to have large fluctuations. But right now it's hard to imagine a change of as much as 100% (ranges from 8 mg-16mg/L in a single day). Just curious.

http://www.grandriver.ca/index/document.cfm?Sec=2&Sub1=7&Sub2=4

Thanks,
Will.

 

[Kit]

Water temperature consistently changing.

 

[wschinke]

Thanks Kit. But isn't it actually the opposite (ie increasing temp = decreasing solubility of oxygen)? The peaks seem to occur in the afternoon, when temps would be highest too.

 

[Kit]

Yeah that's what I mean. Lol.

 

[Dozer]

Yes, warmer water has a lower affinity to oxygen. Not knowing what the answer to your question is, I can only speculate that this is in fact due to aquatic plants photosynthesizing.

 

[[email protected]]

water temps and rate of flow, if the rate of flow is reduced, less DO, faster water has higher DO. with the recent rains, the DO would go up with the increased flow, and drop a little as the flow decreases

 

[chinooky]

The warmer temps mean there is more runoff entering the river. The increased turbulence in the water is essentially dissolving more gases, which more than makes up for lower content in the slightly warmer water

 

[flandogg]

Damn I feel like I'm in school again reading this haha

 

[Polish rifle]

Water at 4 degrees C holds highest levels of oxygen and also has the highest density. Rapid changes in temperature such as the addition of warm run off alters the overall system very rapidly and often. There are other factors however rapid temperature fluctuation has the greatest effect.