You have a few options depending on how variable the water that comes out of your tap is. If all the wells produce low mineral content water then it doesn't matter which well you are drawing from. If your neighborhood gets its water from one well while other wells serve other neighborhoods then you are only dealing with variations in the well you are drawing from. Water from all the wells is pooled then you won't have much variation.
I'd suggest either a chat with the supplier as to how your town's water is distributed and as to how much variation you could expect. If you can't get a satisfactory answer that way then start measuring the hardness and alkalinity using kits or the procedure described at http://www.wetnewf.org/pdfs/measuring-alkalinity.html
. These two parameters won't give you the complete picture but if they are stable over the year it is likely the rest of the parameters are too and conversely.
The ultimate solution is to install an RO system which you may or may not wish to do anyway depending on what's in your water. In removing nearly all the ions RO systems also remove nearly all the variation.