The following two graphics are intended to provide a handy reference describing pH and alkalinity relationships. Clicking on either of the images will open up a high quality PDF file that you can download and print. The source of this information is the excellent textbook from Nalco with the full reference as follows:
Nalco Company. "The Nalco Water Handbook." Third Edition. New York: McGraw-Hill, 2009.
Alkalinity of a Water
The alkalinity in water is the result of mineral salts containing carbonate, bicarbonate, and hydroxide anions, with calcium and magnesium as the positively charged cations (counterions). Knowing the pH of water without a knowledge of the total alkalinity results in an incomplete understanding. Two water samples with identical pH but different alkalinities will respond very differently to the addition of acid. The higher the alkalinity in the water the more resistant that water will be to a change in pH with the addition of acid.