I hope this data will be of interest to some.
The following charts are data from my local water supplier (North Texas Municipal Water District). This data is for the last four years (almost), from January, 2007 through September of this year. The missing data point in the middle of the graphs is due to a duplicated month on the water district's web site.
For some reason, the reports on their web site list the same number for "HCO3" and "Total Alkalinity as CaCO3" from Sept. of 2009 to the present, but prior to that "Total Alkalinity as CaCO3" was about 50/61 of HCO3 which I think is what it should be, so I have taken the liberty of correcting (I hope) the data before making these plots. It looked from the original data that lowering the total alkalinity number was the proper "correction", but I can't be sure. Sorry for the crudeness of the plots, but I don't know Open Office software very well and had to play around to find a way to get the charts from the spreadsheet into a jpg that I could attach here. There is one data point per month - the first one is January, 2007 and the last is Sept. of this year on all charts.
I don't know whether the amount of variation shown here is typical of other water companies, but if it is, is seems to me that a Ward Labs report is only a snapshot which just gives a ballpark water profile, and shouldn't be too heavily relied upon.