The lake water seems very constant, though there are times when you can smell the chlorine strongly. I believe this is seasonal perhaps when they change to chloramines. But I've never tracked it. Or it could be when there's a spike in E. coli bacteria along the lakefront. I don't know if they up the dose of chlorine at that point.
It is common for utilities that chloraminate to switch to chlorination for a short period during the year. This is often in the spring or late winter when the water has less of the reactive content that creates the cancer-causing trihalomethanes. Chlorine has much higher lethality than chloramines and switching over does give the utility a chance to 'shock' the system and reduce any stubborn organisms that were living with the chloramines. Chlorine is much more volatile than chloramine and you will smell the chlorine odor more readily when this switch is on. Most utilities only do this for maybe a month.