Water in Sake: The Element That Makes Up 80%

“Our water here is soft.”

Visit a sake brewery and, more often than not, the master brewer will open the conversation not with rice or yeast but with water. It can seem strange at first. Yet the reason is simple: roughly 80% of the finished sake in your cup is water.

The remaining 20% or so carries the alcohol, sugars, amino acids, and organic acids that give sake its complex character. But by sheer volume, water dominates. That is precisely why the water a brewery uses changes the entire expression of its sake. In this piece, I want to trace, slowly and carefully, how water shapes the flavor of sake.

What Is Brewing Water?

Water Touches Every Stage

Sake brewing moves forward hand in hand with water, from the very first step to the last.

The water used to wash the rice, the water the rice soaks up during steeping, the water that cools the steamed grains, and the water added to the koji, the yeast starter, and the fermenting mash (moromi)—all of this is collectively called shikomi-mizu, or brewing water. During washing and soaking, the amount of water the rice absorbs and its temperature influence how the rice steams and later dissolves. Use poor water at this stage and it lingers as off-flavors right through to the end.

The water that speaks most directly to the final sake, though, is what goes into the moromi. Inside the mash, the yeast ferments while absorbing nutrients dissolved in the water. Water, in other words, is not merely a diluent—it is the very ground on which fermentation takes place.

Warimizu, the Final Adjustment

Freshly pressed sake carries an alcohol content near 20%. The step of adding water to bring it down to around 15–16% is called warimizu.

Most breweries use the same brewing water for this dilution. Blend in water of a different character and the flavor of a carefully brewed sake will fall apart. Warimizu is the final fine-tuning of taste, and here too the quality of the water matters. In recent years, undiluted genshu—sake made without warimizu—has grown popular, and you could say it is a sake in which the character of the brewing water steps directly into the foreground, unsoftened by any addition.

Many Times the Weight of the Rice

Making one sho (1.8 liters) of sake calls for many times that volume in water.

Counting everything from washing the rice through brewing and on to rinsing the bottles and tools, a brewery is said to use 30 to 50 times the weight of the rice in water. This is why sake breweries have always been built where good water flows in abundance. It is no coincidence that so many of the celebrated brewing regions overlap with places blessed by famous springs.

Hardness Governs Fermentation

What Hardness Means

The “hardness” of water is a figure that converts the calcium and magnesium dissolved in it into an equivalent weight of calcium carbonate, expressed in milligrams per liter (mg/L).

By the World Health Organization’s standard, water below roughly 60 mg/L is soft, 60–120 mg/L is moderately soft, 120–180 mg/L is hard, and above 180 mg/L is very hard. In the world of sake, however, there is a custom of drawing the line between “soft” and “hard” at a much lower hardness of around 50 mg/L. Because Japan’s water is naturally soft to begin with, brewers have long marked the divide by their own feel.

Minerals Feed the Yeast

Why should hardness change the character of sake? The key lies in minerals.

Minerals such as calcium, magnesium, potassium, and phosphorus are nutrients for yeast and koji mold. Hard water is rich in these, so the yeast works energetically and fermentation proceeds vigorously. When fermentation runs strong, sugar is steadily converted into alcohol and little sugar is left behind. The result tends toward a dry, crisp sake with firm structure.

Soft water, by contrast, is low in minerals. With fewer nutrients on hand, the yeast works slowly and fermentation proceeds gently. Sugar is more likely to remain, and the sake leans toward a mellow, soft profile with a sense of umami.

These, however, are only tendencies. With the right technique, dry sake can be made from soft water, and mellow sake exists that is made from hard water. Water is an important element, but the final character of a sake is decided by the whole of a brewer’s craft—rice, yeast, and temperature control included.

Nada’s Masculine Sake, Fushimi’s Feminine Sake

The Miyamizu Behind Nada’s Sake

The representative sake of hard water comes from Nada, in Hyogo Prefecture.

What has sustained Nada’s five brewing districts is a famous water known as Miyamizu. It is said to have been discovered around 1840 (the 11th year of the Tenpo era) by Tazaemon Yamamura, the owner of the Sakura Masamune brewery. He was brewing at two locations, Nishinomiya and Uozaki, and although he brewed in the same way at both, the sake from Nishinomiya always came out better. Tracing the cause to the well water of Nishinomiya is the anecdote credited with the discovery of Miyamizu.

Miyamizu is hard, at around 180 mg/L, and rich in minerals such as calcium, potassium, and phosphorus. Thanks to these nutrients, fermentation drives forward powerfully, yielding a dry, taut sake. This character came to be called “Nada’s masculine sake.” On top of that, Miyamizu contains almost no iron, which is harmful to sake. That is exactly why it gives rise to a clean, luminous sake free of off-flavors.

Fushimi’s Gentle Water

Standing in contrast to Nada is the sake of Fushimi, in Kyoto.

The Gokosui spring that rises in Fushimi, chosen among Japan’s hundred finest waters, has a hardness of around 60–80 mg/L—far gentler than Nada’s. With a moderate mineral content leaning toward medium-soft, fermentation proceeds unhurriedly, and the sake comes out mellow, fine-grained, and refined. This is the reason it is called “Fushimi’s feminine sake.”

The saying “Nada’s masculine sake, Fushimi’s feminine sake” was born from this very difference in hardness. Likening the powerful sake of Nada to a man and the soft sake of Fushimi to a woman, it is a traditional expression that has been passed down since the Edo period.

Local Waters, Local Character

Nada and Fushimi are the two extremes, but the celebrated brewing regions all across Japan each rest upon their own waters.

Niigata’s clean, light style is born from the combination of soft water sourced in snowmelt and low-temperature fermentation encouraged by the cold climate. The water of the Chugoku region, passing through granite strata, tends to come out soft, and this leads to the gentle sake of Hiroshima. Tohoku’s clear subterranean streams, Hokuriku’s snow-fed groundwater—the geology and climate of each place decide the hardness of the water and the makeup of its minerals, and that in turn shapes the outline of the sake. Use the same rice and the same yeast, and different water still makes a different sake. That, too, is part of what makes sake fascinating.

Iron and Manganese Are Unwelcome

Among all the minerals, only iron and manganese are unwelcome.

Too much iron turns sake brown and damages its aroma, leading to defects described as an “iron smell” or “sunlight odor.” Manganese, likewise, reacts with light to cause discoloration and deterioration. One of the great reasons Miyamizu is prized as a famous water lies in its exquisite balance: rich in minerals, yet remarkably low in iron.

For this reason, low iron content is treated as an absolute condition for brewing water. Breweries never skip their water-quality testing, guarding sources that are low in iron and manganese.

Good Sake Can Be Made from Soft Water

Sensaburo Miura’s Challenge

Soft water was once considered unsuited to sake brewing. Fermentation was hard to sustain, and the sake was prone to spoilage. Hiroshima, a soft-water region, was thought of as a place where good sake simply could not be made.

The man who overturned this received wisdom was Sensaburo Miura (1847–1908) of Mitsu in Hiroshima—present-day Akitsu in Higashi-Hiroshima. When he took up brewing, he repeatedly spoiled his sake and suffered heavy losses. Searching for the cause, he arrived at the fact that the local water was soft and poor in the minerals that nourish yeast.

After a Hundred Trials and a Thousand Revisions

Miura did not give up. If the water was low in minerals, then he would brew in a way suited to that condition. He raised his koji with great care to strengthen its saccharifying power, and fermented the moromi slowly at low temperatures—layering such refinements one upon another until, around 1898, he perfected the “soft-water brewing method.”

The words he left behind, hyakushi senkai—“a hundred trials, a thousand revisions”—capture his refusal to fear failure and his willingness to keep experimenting. At the 1907 National Sake Competition, Hiroshima’s sake took the top places, proving its strength to the whole country.

This technique of fermenting slowly at low temperatures became the foundation of the later ginjo brewing style. For this, Sensaburo Miura is called “the father of ginjo sake.” That Hiroshima is still counted among the three great brewing regions owes to this lineage of craft that turned soft water into an ally.

Securing Water and Handling It

Why Well Water Is Chosen

Many breweries draw groundwater from wells on their own grounds.

Groundwater holds a stable temperature through the seasons and, filtered by the strata, carries few impurities. Some breweries dig deep wells in pursuit of ideal water. Others, like Nada with its Miyamizu, go so far as to haul water from a source well away from the brewery—that is how much breweries care about water. When brewing season arrives, the low temperature of the water aids low-temperature fermentation and holds back the growth of unwanted microbes.

Filtration and Adjustment

Some breweries use their source water as it comes; others adjust it to suit their purpose.

They may filter with activated charcoal to remove iron and manganese, or use sand filtration to clear away turbidity. Sometimes a touch of mineral is added to soft water to help fermentation along. When tap water is used, the chlorine that harms yeast and koji mold must always be removed. Overdo the treatment, however, and the water loses the individuality that was its own. So most breweries keep their processing to the bare minimum and cherish the quality of the source itself.

Drinking with Water in Mind

Imagining the Water from the Region

Once you become mindful of where a sake comes from, the differences in water begin to show up as flavor.

Taste Nada sake and Fushimi sake side by side. Compare Niigata’s light, dry style with Kochi’s dry sake. You will start to notice that behind each region’s “flavor tendency” lies the water of that land. The place of origin on the label becomes a clue for guessing the character of the water.

The Custom of Yawaragi-mizu

The water drunk between sips of sake is called yawaragi-mizu.

It is water meant to soften the effects of alcohol, reset the palate, and let you taste the next cup afresh. Ideally, soft mineral water—or, best of all, the brewery’s own brewing water. Water accompanies sake both on the inside and on the outside.

In Closing

Eighty percent of sake is water. That single fact tells the whole story of why water matters.

The minerals of hard water enliven the yeast to raise a dry, powerful sake, while soft water calms fermentation to nurture a mellow one. Nada’s Miyamizu and Fushimi’s Gokosui, and the craft of Sensaburo Miura who overcame soft water—each is an individuality born from a dialogue between water and people.

The next time you choose a sake, let your thoughts wander to the water that springs from that land. Dissolved within a single cup is the story of the ground that water flowed through.

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Learn more about sake production in How Sake is Made or Sake Yeast Types.