We rate highly cities with abundant fresh water and effective delivery systems.
Fresh water is generally characterized by having low concentrations of dissolved salts and other total dissolved solids. wikipedia 
Much of the surface fresh water and ground water is unsuitable for drinking without some form of purification because of the presence of chemical or biological contaminants.
Water supply systems get water from a variety of locations after appropriate treatment, including groundwater (aquifers), surface water (lakes and rivers), and the sea through desalination. wikipedia
What rating system approaches effective delivery, treatment, stores such as aquifers and wells, "surface water" online?