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April 30, 2007


Issues of water as global resources

okisan.jpg Copyright JFS

Lecturer: Taikan Oki, Professor at Institute of Industrial Science, The University of Tokyo

The Earth is called the "water planet." However, 97.5 percent of water on the earth is saltwater and considerable ratio of the remaining 2.5 percent, fresh water, consists of snow and ice. Therefore, water available for human beings is extremely limited. But, it is not appropriate to understand that the total volume is insufficient. We should compare the volume not with the one the whole planet has but with the one human beings are in need of. Furthermore, we should recognize water not as "stock", but "flow" in economic terminology. Use of water means a process of taking in a part of circulating resources as a flow and then returning it to nature.

Water shortage does not mean shortage as a substance. Like money, water is unevenly distributed and therefore enough water is not supplied to some people on the earth. How we solve this maldistribution is the key to solve the water problems. Then, why does water shortage occurs in reality and what is needed to solve the problem? We would like to tackle these issues today.

Two indices to measure the degree of water shortage

There are two indices used to measure the degree of water shortage. One of the indices is "water resource availability." It represents how much water is available to a person annually within the volume of rainwater that did not evaporate and flows into rivers or soaks into grounds to be groundwater. When the volume is less than 1,000 cubic meters, the situation is thought to be under stress that people cannot use water enough.

Another index is the ratio of water consumption against this availability. If the ratio exceeds 0.4, the situation is thought to be under severe stress.

One person annually consumes 500 cubic meters in developing nations and 500 to 1,000 cubic meters in developed nations. Among them, America is an exceptionally heavy user and one American consumes 1,700 to 2,000 cubic meters annually. If it is converted to daily consumption volume, one person uses as much as 500 liters in such nations as Australia and the U.S., while the world average is approximately 170 liters. One Japanese consumes 320 to 330 liters under the same conditions.

Water does not disappear - water as "flow" resources

Out of 320 to 330 liters, daily consumption of water per capita in Japan, approximately 250 liters are consumed by individuals at home. One-fourth of the volume is used for bathing, toilet cooking, dishwashing and laundry respectively. Meanwhile one person needs only two to three liters of drinking water per day. In other words, hundredfold of drinking water is used for the purpose of "washing." As for household water, it is not an exaggeration to say that water consumption means washing dirt away.

Consumption of water does not mean decomposition into different materials like petroleum. Water does not disappear as a substance. In other words, if technology, energy or cost to purify water is available, it can be recycled.

Maldistribution of water

Water is recyclable resources and thus does not disappear. The earth has far more water than the volume human beings need to use. Despite this fact, water shortage crisis does arise. It is because water is unevenly distributed in terms of time and place.

There are two types of maldistribution; one is the temporal one like seasonal variation and the other is the spatial one where water is affluent in one region but insufficient in another. As it is difficult to bring water over boundaries or to different basin, spatial maldistribution is seldom evened. A plan to direct water of the Shinano River in Nigata Prefecture to Tokyo has been long discussed but has not been realized. Human society is not influenced solely by economical reasons.

Population increase, or urbanization, may trigger off water shortage that did not exist. People concentrate in large cities, without taking account of supply capacity of water, energy and food. A region may have a population in some phase of growth that can be supported in an average year but cannot in a dry year. This causes water shortage.

Virtual water - Relation between Japan and global water resources

Food production requires large amount of water. This is the case not only for grain production but for meat production. Cattle drink water and livestock barn needs to be washed, but much more significant fact is that meat production requires tremendous volume of grains for animal feed, which requires huge amount of water in growing. When a country imports food, it doesn't need to consume a large amount of water to produce it. For countries suffering from constant water shortage, importing food means importing water. In terms of water resource, it is recently called virtual water trading. Virtual water refers to the water used in the production of food, goods and services. Japan's food sufficiency rate is less than 40%, which means Japan is a leading importer of virtual water.

The volume of water needed for grain production includes evaporation and is calculated from the time to harvest and the volume of harvest per unit of land area. It is estimated that in rice production water of approximately 3,600 times of the edible part is required (in weight). For stock farm products, it is calculated from the growing period, or time to market, the amount and the type of livestock feed and the volume of meat taken from one farm animal. It will be 4,500 times for chickens, 6,000 times for hogs and 20,000 times for cattle.

If Japan has to domestically produce main staples which are currently imported, approximately 60 billion tons of water would be required annually. In other words, we are currently saving the amount of water almost equivalent to the annual amount used for total domestic irrigation (57 billion tons). We drink one ton of water at the maximum, and consume approximately 130 tons of domestic water, the same volume of industrial water and approximately 500 to 600 tons of agricultural water. This means we are dependent on water outside Japan, the amount of which is almost the same as the annual domestic agricultural water or more than 40 percent of the total annual water consumption (1,250 tons). Now, you understand that Japan's water resource issue does not limit its scope to home but is dependent on the water resources across the world.

When we look at the world's bilateral trade of virtual water related to main grain only, it is predominantly exported to the Middle and Near East and North Africa. They are the areas that have less water resources in their natural environment. They are under serious water stress if we ignore virtual water, but they can supplement the shortage using the mechanism of selling oil and buying foodstuff.

As of 2000, 23 nations are categorized as the ones under serious water stress. Economically rich nations resolve the water shortage problems using virtual water. Poor nations cannot take any economic measures and thus are forced to be in continuous shortage. Originally, virtual water should be a tool to analyze this kind of situations and determine which areas are in serious water shortage.

What the future will be like?

When we predict the future of water resources, we need to consider the change in both supply and demand. Change in demand includes population increase and economic growth. The stronger the economy is, the more water is required, as the diet tends to be shifted from grain to meat, resulting in increased water demand.

As for change in supply, a slight increase in water resource availability is expected due to climate change and other reasons. Still, there are some concerns. There is a prospect that Europe, which was originally pastures, typically France and Spain, will have less amount of water storage. This is a grave problem that will affect food demand and supply.

But the situation is not always becoming worse. It would be widely known that some parts of the Yellow River in China once dried up. The situation was most serious in 1997, when 700 kilometers dried up for more than 200 days. Since 2000, however, no dry-up has been observed, even though some parts have only a narrow stream like a brook. This is a remarkable improvement. In the past, they had no such idea as water intake management in the total drainage basin. By managing water intake volume and doubling the water price which had been too inexpensive, they prevented the water flow from stopping after 2000.

If we turn our eyes to the relation between GDP and the volume of industrial water intake, the ratio of quantity of water taken against industrial output is extremely smaller in Japan than in other nations. In addition, the water recycling rate is almost 80 percent on average across all industries in Japan, which is surprisingly high. When I discuss this matter with water resource specialists outside Japan, they wonder why Japan does not try to attract attention to it. Water consumption in China will further increase, but it can be further reduced if they introduce the recycling technology of Japan. This is a favorable factor.

Water, energy and foodstuff - keys to a sustainable society

As long as I am a specialist of water, I talk about water today. But, it is not sufficient to consider only the aspect of water if we want to realize a sustainable society. Specialists of energy and foodstuff would consider their own discipline only. In reality, however, the three fields are tightly integrated and we should consider them comprehensively. Although the biofuel has become very popular, we should not forget the fact that it is an energy source converted from foodstuff and that production of foodstuff needs large quantity of energy.

If a nation has affluent water, it can produce energy through water power generation. If another nation has affluent energy, it can produce fresh water using it. Food production requires a larger amount of water for irrigation. A region can supplement water shortage by importing foodstuff from other regions -- this is a concept of virtual water.

Which region has sufficient or insufficient amount of water, energy and foodstuff? We need to analyze the situation based on the three factors. Such viewpoints will be widely understood in future as how the three factors should be distributed or which factor is the bottleneck in realization of sustainability.

There is a Chinese proverb that says, "You should not forget the person who helped you." It originally meant that you must think about who dug the well when you drank water. I would like to give you a new version of the old saying I invented as a conclusion of today's lecture. "People should always think about water when they eat and drink."


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