2008 Zaragoza International Exposition “Water Tribune” Symposium Special Lecture by His Imperial Highness the Crown Prince of Japan

(1) Scene with windmills

Don Quixote and Windmill

Don Quixote, the classic novel by Spain's great writer Cervantes, is much loved in Japan. The passage where Don Quixote, accompanied by his faithful ‘squire’ Sancho Panza, gallantly tackles the long-armed giants never fails to arouse the curiosity of children of every age (Figure 1).

The giants are, as Sancho Panza rightly points out, windmills to turn the millstones. Don Quixote spurs on his poor old horse Rocinante to attack the giants. But a sudden gust of wind turns the windmills' big sails, throwing Don Quixote to the other side and his steed to the ground.

During my visit to Spain I went to La Mancha to see the windmills. With their work long done, the white windmills now stand motionless on the sunbaked red earth. But as I watched them carefully, those blades looked like giant's arms. I could well imagine how they served the local people in Cervantes' time.

Dutch Windmills

Windmills, of course, remind us of those in the Netherlands, the country of HRH Prince William-Alexander, the Chairman of UN Secretary-General's Advisory Board on Water and Sanitation (Figure 2). In the Netherlands windmills are symbolic of man's contest with the water. The windmills were essential for protecting and extending the land, a quarter of which was below sea level, by draining the water out to sea by lifting it from channels crisscrossing the reclaimed areas.

This photograph shows a group of three windmills in Leidschendam, a suburb of The Hague. It is a little difficult to see, but on close examination we can discern how the water level is actually higher than the dry land. By harnessing the wind that blows throughout the year from the North Sea the Dutch were able to drain the water and so develop the land.

(2) The role of waterwheels

Waterwheels in Spain

In Spain, waterwheels were used to turn stone mills to thresh the grain and for flour-milling. Now, back once more to Don Quixote. He is with Sancho Panza in a small boat on the Ebro River and imagines a large waterwheel in the river to be a castle where a beautiful princess and some knights are held captive. He gallantly attempts to rescue them but Don Quixote is twice pulled to the bottom of the river. Finally, soaked to the skin, he is pulled out by some millers (Figure 3). The illustration vividly shows the situation of the little boat that is pulled by strong stream to the waterwheel. We can laugh at Don Quixote's foolhardiness but our attention is also drawn to the power and danger of the water.

I took this photograph on an earlier visit to Toledo (Figure 4). Although we cannot see it in the photo, there is a ruin of a huge facility combining a number of waterwheels to draw water from the River Tagus (Tajo) to the city 100m higher than the river near the Alcantara Bridge at the foot below the Alcazar of Toledo. I learned that it was the creation of Juanelo Turriano, a clock engineer and mathematician who came from Italy in the 16th century. The model is exhibited in the Castilla-La Mancha Pavilion at the Expo site (Figure 5).

The citizens of Toledo had to collect rainwater or fetch water on the backs of donkeys from the river before the installation of the facility. Unfortunately, the original plans with which one might have studied the details of the project have been lost, but enough remains for us to marvel at the ingenuity of humans who have sought to use the power of water to sustain life.

Waterwheels in Japan

Waterwheels played various roles in Japan as well. Their history is long. Japan's first history book, Nihon Shoki (Chronicles of Japan), compiled in 720 A.D. records that in March 610, in the 18th year of the reign of Emperor Suiko: “A Mizuusu has been built. The construction of Mizuusu would begin then” (Figure 6). A Mizuusu is a stone mill using power of a waterwheel. It is said that the technology of Mizuusu was transmitted by the monk Don-cho who was dispatched to Japan from the king of Koguryo (an ancient state in the north of the Korean peninsula).

In the Yoro Ryo, a government decree proclaimed in 718, (that was described in the Ryo no Gi Ge, which was issued in 833 during the Heian Period), there is an entry on irrigation in a section titled Zoryo (miscellaneous rules). It is believed that the entry Mizuusu refers to waterwheels. Or it may be that the use of the waterwheel was encouraged in order to harness water as a source of power to strengthen the economic base of the country as it embarked on nation-building after importing the administrative system of Tang China. We know little, however, about how much waterwheels were used.

Later, at the end of Kamakura Period in the early 14th century, the Ishiyamadera engi emaki (an illustrated handscroll of the legends of Ishiyamadera temple) contains an illustration of waterwheels lifting water into rice paddies (Figure 7). The bridge in the illustration is considered to be the Uji Bridge, one of the three famous old bridges in Japan. The river that flows out of Lake Biwa, the largest lake in the country, starts out as the Seta River, then changes its name to the Uji River as it flows through the southern part of Kyoto and from there as the Yodo River to Osaka Bay as the Yodo River. All three rivers are recorded in history. The waterwheels of the Uji River appear in various paintings and in the literature of the Middle Ages. They are believed to have been built by members of nobility and by large shrines and temples. This is further evidence that waterwheels were prevalent in Japan by this time.

Towards the end of the 18th century during the Edo Period, a group of waterwheels at Asakura (present day Asakura City in Fukuoka Prefecture) were in active use. Here you see waterwheels in Hishino (Figure 8). Three 5-metre-diameter wooden wheels in a cluster formation are drawing water with great force. They represent state of the art irrigation engineering of the day, helping to develop new rice paddies in an area prone to drought. Now, more than 200 years later, these waterwheels are still in commission and irrigating local paddy fields.

(3) Contemporary use of wind and water power

In this way, wind and water played a big role as valuable energy sources until steam engines were adopted for general use. What can we learn from the early use of wind and water power?

Wind power generation, while providing only a modest amount of power generation, now has an installed capacity growing in excess of 25 percent a year in the world. Spain appears to have kept up the windmill tradition which is described in Don Quixote. The installed capacity of Spanish wind power generation is one of the largest in scale in the world along with Germany and other countries, and is increasing at a rate of over 30 per cent every year (Figure 9).

The amount of hydropower generated worldwide is about the same as that produced by nuclear power plants. In Japan, hydraulic power generates about 90 billion kilowatt hours (kWh), accounting for about 10 per cent of the total power generation. These are examples of how tradition, nourished by history and natural environment survives the test of time (Figure 10).

Energy is one of the challenges that now requires global attention, while we all remain committed to meet the pressing challenges posed by the rising world population and global warming in a sustainable manner. The purpose of this lecture is not to search for answers to these challenges. These are issues that must be continuously addressed in a comprehensive manner with a long-term perspective. However, it may be of great significance for the future of mankind if we can learn from the wisdom and ingenuity of our ancestors in utilizing the natural energies of wind and water to develop technologies that are appropriate to our present and coming times.

(1) Roman aqueduct (Segovia, Spain)

During the Roman period, water systems were constructed in many cities in Europe that compare well with our modern ones. There are many ruins of the old water conduits in Spain as well. The aqueduct in Segovia that is said to have been built in the late 1st or the early 2nd century is known to many Japanese (Figure 11). I visited there in the summer of 1985 and was struck by the immense height of the aqueduct that spoke of the importance of water to the Romans, and their long-term vision of maintaining reliable water supply.

The Romans built public baths throughout their empire, distributing huge amounts of flowing water. The scene of all of people such as soldiers and citizens enjoying the baths after a hard day's work gives one a vivid insight into the lifestyle of the Romans in those days. The abundant flow of water also enabled the functioning of the extensive underground sewer system, contributing greatly, one supposes, to maintaining the sanitary condition of the city state.

(2) Water Palace (Alhambra Palace, Spain)

Some thirty years ago I visited the Alhambra Palace as a high school student. The grandiose complex overlooking Granada is an awe-inspiring sight (Figure 12). What struck me most, though, was the central importance of water in Islamic civilization. The water gardens designed to create an image of paradise in the Generalife Detached Palace, although the surrounding area did not possess enough water, left me with a profound impression (Figure 13). This was another scene that had a profound impression on me. I can still hear the sound of water in the fountain in the Lion's Patio and the tranquility of the Royal Palace enveloped in darkness after nightfall.

The Alhambra Palace is a fusion of two civilizations, Islamic and Christian, nurtured in the arid region. I can not help feeling that the sound of the fountains makes one think of the spiritual relationship between man and water.

(3) Curious spherical object in a Paris sewer (Paris, France)

In Paris I visited the Sewer Museum that is housed inside a mammoth sewer. I was immediately struck by a large and strange spherical object (Figure 14) that I was told was made for the purpose of cleaning the huge pipe laid under the Seine River. It is a ball made of wood and is slightly smaller in diameter than the duct. When the ball was introduced into the duct, a siphoning pressure propelled it along, scrubbing the wall with spurting water in the narrow gap between the wall and the ball. I was explained that in this way the ball and the spurting water would wash away dirt and filth as it traveled in the duct.

A replica of the ingenious ball that was presented to me at the time as a memento of my visit sat on my desk for a long time. Every time I looked at it I was reminded of the wisdom and ingenuity of Parisians who recognized the importance of constructing and maintaining the sewer system as an essential infrastructure for providing citizens with good urban sanitation.

(1) Chisui for regional development (Ishiibi Intake, Saga Prefecture)

The Edo Period that began in the early 17th century saw a great deal of new paddy development under the Tokugawa Shogunate (central government) and the clans (local governments), far more than in the preceding Sengoku (warring) Period.

Here you see the Saga Plains in Kyushu, the southern island of Japan (Figure 15). The Saga Plains had been hit by flooding from steep mountains whenever there were heavy rains, while at other times prolonged drought conditions brought water shortage and suffered to the people. It was a very severe environment. Some 400 years ago, in an attempt to improve the situation, Naridomi Hyogo Shigeyasu, the chief retainer of the Saga clan, built a intake that enabled them to direct water from the Kase River to the Tabuse River, thereby supplying the Saga castle town with water for agricultural and household use (Figure 16).

The Ishiibi Intake is a product of several contrivances. The weir tamed the flow of the Kase River (Figure 17), gently made back flow and redirected the flow to the Tabuse River. For this purpose, Naridomi built the Ooidetodate (a weir), islands with stones, and Suisei (piers from the riparian towards the centre to moderate the flow of water) in perfect harmony. Sand and silt would be deposited on the bottom and clear and clean water would be supplied to the town through an aqueduct.As a result, Saga residents were able to enjoy the good-quality river water for drinking even as late as the Meiji Period.

To mitigate negative impacts of these structures on flood management, the embankments were double lined to create a space between them to retain water during a time of flood. In addition, bamboo was planted in the flood retention area in order to weaken the force of the flood water and prevent stones and driftwood from being washed downstream. Usually, it is very difficult to achieve a balance between flood protection and water use, but here both purposes were effectively served simultaneously solving two challenging issues.

The Ishiibi Intake protected the Saga Plains from the two water hazards, flood and drought, for 350 years until a new sluice gate was built in 1960 to draw water from the river. Because of its historical value, the Ishiibi Intake was restored three years ago following a thorough excavation study. As a result, we can see the original shape of the Ishiibi Intake today. Even though there was no such term as “river engineering” when it was first built, the wisdom and skill of the local people were fully utilized.

(2) A Siphon in the Sky (Tsujunkyo Bridge, Kumamoto Kumamoto Prefecture)

This is the Tsujunkyo aqueduct bridge built in 1854 (Figure 18). It is a 75-metre-long 20-meter high stone bridge, with a water flow of 15,000 cubic meters a day. It is still in service watering 120 hectares of agricultural land.

The Shiraito Plateau in Kumamoto Prefecture in Kyushu, is an elevated area 400 to 600 meters above sea level that historically suffered from drought. Available water in this area was only from ponds and springs. Fuda Yasunosuke, a village headman, took the lead and decided that a waterway should be built to supply water to farms and households. He proposed an ambitious plan to draw water from the Sasahara River some six kilometers away and transport it in 12 kilometers of irrigation channels across hills to irrigate existing farmland as well as to develop new land for agriculture (Figure 19).

The aqueduct bridge had to cross a valley chiseled deep by the Gorogataki River. Experienced local stonemasons and farmers from neighbouring villages participated in this project which has many lessons even for us today. With the successful mobilization of these workers, the work was completed in only twenty months.

The aqueduct bridge has many innovative features. You can see some people on the bridge watching flushing water. This flushing water is not just for entertaining tourists (Figure 20). Of course, it is not a great leakage of water. It is for removing mud and sand from the conduit with the aid of the flowing water.

A bridge for the conduit to span a 30-metre-deep gorge was beyond the skills of the masons of that day who could only manage one 20-metre high, so the bridge was built at that height. The problem of raising the water the extra 10-metres was solved by siphoning with hydraulic pressure. The bridge is therefore a unique combination of an aqueduct bridge and a siphon (Figure 21). The aqueduct faces strong hydraulic pressure due to the siphon structure. By using this hydraulic pressure and flush water, mud and soil in the aqueduct have been cleaned. This beautiful arc is the result of this maintenance skill (Figure 22). To ensure long-term use of the aqueduct, the designers even included the mechanism for its maintenance.

The scale of this aqueduct bridge is hard to compare with that of the one in Segovia, but it does demonstrate the practical wisdom of the local people, an asset which is common to both East and West.

(3) Edo, a recycling society

Let me take you to Edo, which was one of the major cities in the world in the 17-19th centuries. Edo, the old Tokyo, possessed a unique and highly practical night-soil disposal system. Night-soil from every household was collected by ships using the waterways that traversed the city, and transported to nearby farming villages via rivers and canals (Figure 23). It was carried in special “night-soil barges” and treated (and bought) as a valuable fertilizer (Figure 24). Farmers stored it in tanks for fermentation and used it as fertilizer after the heat of fermentation had killed off parasitic worms and other micro-organisms.

Rice and vegetables grown in the farmlands were transported back to Edo by water transport. In other words, there was a functioning resource recycling system linking the large city of Edo and the outlying farmlands. It is no wonder that visitors to Edo from overseas remarked that it was the world's cleanest city.

This is the International Year of Sanitation. The subject of sanitation has been neglected, and treated more as a taboo than as an important issue that relates to human dignity. What are we doing about this? Our wisdom is now being tested. The Edo night-soil recycling system may not be replicated easily in our modern societies. But the fact that such a society did exist in the past may encourage communities suffering today from lack of sanitary facilities to use their imagination to create a night-soil recycling system best suited to their conditions.

(4) Water Cycle in the Tokyo Metropolis

We have looked at how the Japanese related to water in the past, but what are we doing today? Mass production, mass consumption and mass waste disposal are features of our contemporary resource-wasteful society. This applies also to water. We tend today to use water wastefully, forgetful of how precious it is. We should remind ourselves of patient efforts that go into supplying the water we use and treating the wastewater we produce in a sustainable manner.

Tokyo's waterworks aiming at a reliable supply of water

Let us look at what is happening in Tokyo's waterworks. The city's water system includes an immense network of about 26,000 kilometers of pipes in addition to reservoirs, dams, water treatment plants and water supply services. Looking at this map that shows in red the city's network of pipes of 40 centimeters or more in diameter, one can see the resemblance to our own circulatory system (Figure 25). Water loss through leakage of 3.3% in FY2007 is quite amazing as losses of many world major cities are above 30 %. Water leakage in underground areas is difficult to ascertain and electronic leakage detectors are used to locate any sound of leaking water after the city has gone to sleep (Figure 26). I tried it, and I can tell you, it was really arduous work. It is this kind of conscientious service that has gradually reduced the leakage rate. In addition, I am very happy to hear that these skills have been transferred to many overseas countries.

We cannot, of course, overlook the maintenance of the sources of our water. For over 100 years the Tokyo metropolitan government has been making great efforts to maintain and nurture the forest reserves in the watershed. Today, the Tokyo Metropolitan Government conserves and develops 21,600 hectares of forest, equivalent to 35 per cent of the Tokyo's 23 special wards area, for the purpose of protecting its water resources and purifying water (Figure 27). Efforts are being made to gradually diversify the forest from a single specie of coniferous trees to include Mizunara (Japanese oak) and maple. The mixed forest enriches biodiversity and creates soil more suited to sustaining water resources as well as purifying water quality.

Tokyo's watershed forest extends into neighbouring Yamanashi Prefecture. I went there recently and took this photograph of the forest that spreads towards Mount Daibosatsu (Figure 28). Tokyo's watershed forest also includes Mount Daibosatsu. Some parts of the area were once devastated land, but now they are richly forested (Figure 29). When I closed my eyes and listened I could hear the birds singing and the streams flowing down the valley. The Tokyo Metropolitan Government has created a path through the area to remind people of the function of the water-nurturing forest as well as their responsibility to protect nature. I left the area well pleased that the forest that is so essential for our water and thus for our lives was being well watched over by the good people who are involved (Figure 30).

The Tokyo Metropolitan Government is expanding its initiatives overseas. Metropolitan staff members are being sent abroad, while trainees are invited to Japan. A website has been set up to share information on water services related technology. I believe that it is important that Japan's waterworks engineering skills could, if required, be transferred to needy areas through partnership with local governments who are directly in charge of maintaining and managing water services.

Rebuilding the urban water cycle - reuse of treated water from the sewerage system

Now, what about the other important urban water recycling issue - sewerage? I would like to touch upon a pressing and present issue of the sewerage system. A reliable supply of water and appropriate water treatment are the life-lines of any city. Increasing population and urbanization all over the world is challenging already strained urban water supplies and management. Moreover, the water shortage that is expected to be worsened by climate change is yet another threat to the sustainability of many cities. There is a growing need for urban water systems to become cyclical and self-sustainable.

It follows that measures to reuse city wastewater have taken on increased urgency, and various initiatives are being implemented in Japan. For example, in Tokyo, 3,000 cubic meters of wastewater, after treatment with the most advanced technology at the Ochiai sewage treatment plant, is sent every day to the Water Recycling Center in Shinjuku, a sub-centre of the capital, to be reused for flushing toilets in high-rise buildings (Figure 31). The recycled water also feeds urban rivers to restore the urban environment (Figure 32).

We Japanese have a culture of recycling water many times. In our homes, water used for cooking is used to mop and clean, and then to water the garden. This spirit may be reflected in our dedication to the advanced treatment of sewage and its use for purposes that best suited to the quality of the treated water.