Odd Water Chemistry question - pH and winter/cooler climate

[windsurfnut]

I have an odd (to me) water chemistry question.

 

For starters, we draw from a Lake to fill our tub. Other then establishing a sanitzier base (Bromine) and water on the softer end of the scale, we need to do little in terms of Alkalinity and pH balance.  Small adjustments after a fill and we're usually stable.  

However, something seems to change in the fall.  We have a very difficult time managing pH levels.  They skyrocket, and lowering them with pH Minus them only results in raised levels shortly after.  It only happens once the weather gets colder.    Last year we had a theory that once the ice formed on the lake that the water chemistry must be affected as we draw the water from below the ice.  Same thing has happened this year and we are not yet frozen over.  Nothing else changes, our frequency of use doesn't change, same bathing suits.  

We're confused why we have to chase pH levels now, and yet its stable all summer.  In both all seasons, a fresh fill results in the same.. Summer stable pH, fall/winter raised pH.  

Any insight as to why this is would be appreciated, as would any recommendations on how to address this issue.

[waterbear]

IF the TA does not change then my guess is that the pump is running more in the winter to maintain the temperature resulting in more outgassing of CO2  from additional aeration, which is the main reason for pH rise in a hot tub or pool. Your actual TA readings in both winter and summer would be helpful.

IF you are having problems with the pH riseing then lower your  TA. 50 to 70 ppm is a good starting range.

If the TA is different when the lake water is colder then please post the values at the different times of the year.

Read both of these for better understanding of the relationship between TA and pH rise:

https://www.poolspaforum.com/forum/index.php?/topic/52522-some-truths-about-ph-and-ta/

https://www.poolspaforum.com/forum/index.php?showtopic=28846

(Your duplicate post has been deleted)