This map provides a general indication of the softness or hardness of regional water supply, based on calcium carbonate levels. To fully understand the makeup of your water requires further analysis of dissolved metal and salt concentrations, particularly in the context of coffee brewing and extraction. (Ion concentrations to look at include those of magnesium, calcium, bicarbonate, chloride, sodium, and potassium).
Check out our article on filtration options for the café for a few more ideas on how to better regulate your water supply.
Table adapted from and prepared by the United States Geological Survey.