Making good sake requires good water. Since ancient times, good Japanese sake has depended on the water, rice and climate. "Miyamizu" (shrine water) of Nada, Hyogo Prefecture in Japan is famous as the perfect water for fermentation of sake, and it is said that the technological factors behind Nada's success in the sake industry have been its highly polished rice and use of Miyamizu. When conductivity is calculated from the quality table of Miyamizu, it becomes 600 µS/cm, which means that is delicious water. It is further said that Miyamizu was discovered by Yamamura Tarozaemon, an ancestor of Sakura Masamune, in 1840. Tarozaemon carefully examined the difference of taste from one place of fermentation to another, and through trial and error by changing chief brewers and comparing methods of fermentation, he finally found the water to be a key factor in the taste of sake. Today, it is clear through analysis of Miyamizu which components in the water affect fermentation, and more and more brewers have came to use water that is appropriate for sake fermentation. Still today in Nada, Miyamizu is used, and the region takes great pride in the taste of its sake. Naturally, when making whiskey, wine or beer, there are differences in taste and color, depending upon where they are produced and what kind of water is used. The famous Munich black beer uses hard water, and Pilsner light-colored beer uses soft water.

When ice produced in a home freezer melts, does its conductivity return to that of tap water?

When water freezes, it freezes from its pure portion and from its surface. Because of this, the conductivity of the outside part of an ice cube goes down because impurities migrate away from the surface during freezing. Conversely, the center portion of the cube contains a concentration of the ions and pollutants that were contained in the original tap water, and therefore exhibits higher conductivity. Accordingly, when you drink juice or whiskey with home-made ice, try to drink it before the ice melts completely, and the original taste will not be adversely affected (although it will be slightly diluted).

When looking at the color of river water, many people may think that if the water is transparent, it must be clean. But having read this far, you may wish to reserve judgment until you have measured the conductivity of the river water.

Let's now compare the conductivity of water in a river with its dirtiness. By measuring the conductivity of river water, we can obtain a rough guide as to the concentration of ions in the water. However, the ions contained in river water are originally and predominantly the components of the soil with which the water is in contact, and because of differences in the soil, the conductivity of river water differs from one river to another. Therefore, the degree of conductivity of river water alone does not tell how dirty the river is.

There is a saying "The water must be clearer three feet downstream," meaning that the river itself has the capability of getting rid of dirt and is somehow helpful in the dilution, deposition, absorption or penetration of pollutants, as well as purification with microbes. These actions differ from one river to another, and although the conductivity does increase generally as we move from upstream to downstream, conductivity downstream is sometimes lower, thanks to purification.

Recently, however, residential sewage and industrial waste flow into rivers in amounts that far exceed any river's capacity for self-purification. Rerouting of a river can also sometimes compromise its purification capabilities. As a result, rivers in general have become polluted, and in many cases, conductivity is higher downstream.

Rain is another thing to consider when talking about rivers.

Compared with river water, rainwater has lower conductivity, and depending upon the season, river water may be diluted or enriched. In Japan, conductivity is low in many places during the rainy season of June and July. With this taken into consideration, when judging the dirtiness of a river by its conductivity, it is necessary to fully understand the characteristics of that river. We must make a global judgment by not only knowing its characteristics upstream and downstream, but also how the river changes on a long-term basis rather than making a one-time judgment.