Abstract
Kumamoto City is a worldwide exceptional urban area where 100% of its water supply comes from groundwater; however, reductions in groundwater amount and nitrate pollution level are current concerns. In this study, the water quality characteristics of well water samples collected in Kumamoto City were investigated. Most of these samples showed water quality characteristics of the “alkali metal-bicarbonate type”, which are typical of Japanese groundwater. They also contained equivalent amounts of Ca2+, Mg2+ and Na+. The well water samples were divided into 11 large groups on the basis of their water quality characteristics related to groundwater flow. No significant change in the water quality of wells in Kumamoto City has been observed over the past 20 years except for a few wells. From the results of a water tasting test, the taste of Kumamoto City tap water was considered to be the same or better than that of commercial bottled waters, and a truly tasty water index (TTWI) was established on the basis of the relationship between the water characteristics and the results of the water tasting test.
