I have been doing some prospecting for gold this year and have been using the USGS site to check water depth and turbidity (clarity). Here is their page for the Vermilion River water height. We had some rain last night and you can see the water went up a few inches. It will drop back down in the next day or so like I would expect. Now scroll down a bit and you can select other parameters like pH, dissolved oxygen, turbidity, etc. Select pH and then dissolved oxygen. Hmm, they both go up and down sinusoidally every day. I wonder why?
I see water temperature goes up and down also. maybe the dissolved O2 just follows. But if you select a 30 day span they don’t match the water temperature so closely.
I would guess that this is related to photosynthesis - carbon dioxide causing acidity.
ETA: I tried to look at the site to see if pH rises during the day, which would be consistent with photosynthesis consuming carbon dioxide and releasing oxygen, but you can’t tell the time of day from the axis.
True.
But increasing photosynthesis = increasing acidity = falling pH.
Another factor relating pH and temperature is the disassociation constant of the minerals carried by the flow say CaCO3 (insoluble) + CO2 + H2O <-----> Ca++ + 2HCO3-
CaCO3 is less soluble in hot water than in cold water ie precipitation
Conversely, an increase in water flow will favour disassociation.
There will be more photosynthesis in clear water than turbid water. There are algae everywhere, growing on any underwater surface, not only when they are obviously visible in blooms or mats. And surely some vegetation, rooted aquatic plants.