Chapter 2　Water Condition

　Annual rainfall in Japan is approximately 1,700 mm. Average annual rainfall in the world is approximately 970 mm, so it seems that Japan is high rainfall area where is rich for water. However, Japan has small national land and high population density. Thus, to estimate the water amount for one person, it can't be conclude that Japan is rich for water.

Comparison of rain water amount in the world（Calculation）

Country	Annual Average rain wate amount（mm）	Rain amount per one person(/year・people)
Japan	１，７００	５，１００
the United States	７６０	２５，６００
Canada	５２０	１６７，１００
China	６６０	５，０００
Saudi Arabia	１００	９，９００
World Average	９７０	２１，８００

Reference　Ministry of Land, Infrastructure, Transport and Tourism ＨＰ

　Moreover, 2/3 of Japan national land is mountain so that rivers are steep. Also, the amount of rainfall depends on season. Even though we have large rainfall amount, there is not so much water that we can use. We have floods by temporal storm rainfall at typhoon season, while we must regulate water supply due to lack of water when little rainfall season. To calculate dam usable storage amount per one person, it is 1/17 of America and 1/16 of Korea.

Comparison of Dam storage capacity in the world

Country	Storage amount （million ｍ３）	Population （ten thousand people）	Storage amount per one （m３）
Japan	３，９７０	１２，３９２	３２
the United States	１３５，２４２	２５，２６９	５３６
the United Kingdom	２，５６８	５，７３７	４５
Canada	１７，５００	２，７０３	６４７
Korea	２１，６１９	４，３２７	５００
Taiwan	１，３３５	１，９７０	６８

Note　１） The population was calculated in 1991, which is in "理科年表１９９４年 (Science timeline 1994)"
　 　　　　except Taiwan （’９０〜’９１ 世界国勢図会, Wolrd Census）.
Note　２） Dam data was from "国際大ダム会議の台帳 (National dam conference)"
Note　３） Total storage amount is the total water use of dams including tap water.
Reference　Ministry of Land, Infrastructure, Transport and Tourism ＨＰ

　Vapored water from the surface of the earth stays in the atmosphere, and then it falls down on the ground as rain or snow. On lands, the water flows and it washes the surface of grand. By dissolving substances, water amount gradually increases and small brooks will be mighty rivers which will be then connected to the ocean. Moreover, water which penetrates under the ground becomes subsoil water or underground water.
　In Japan, water resource has been effectively used for rice paddy and for dam. Currently, underground water has been used for industrial water.

　Water penetrates in rocks as rain or snow, and then water gradually dissolves minerals contained in rock. Water stays for a while and then becomes spring water which contains minerals (Calcium or Magnesium). Depending on mineral amount, the water is regarded as soft water or hard water.
　Since underground water in Japan stays on the underground for short time, it has little effect from minerals. Thus, the most water in Japan is soft water. On the other hand, water in such as Europe where there are lots of lime rocks stays for long time, thus it becomes hard water which contains lots of minerals.
　In Europe, there are water which is over 300 hardness, so Japanese people who don't get used to hard water tend to suffer from diarrhea. The reason why people in Europe don't drink water directly is the hardness of water. Moreover, soap don't beat up due to the water. That is because hard water contains lots of calcium and magnesium and they combined with fat acid in soaps and settle down as the substance which doesn't dissolve by water.

　The water difference affects on food. Since hard water contains lots of minerals, it is not suitable for food. Thus, in western-style food, people steam or fly up by oil rather than boiling by water. Moreover, they use milk or wine for boiling. In Japan, people has used water for stew, soup, and boiled food for long time.
　In alcohol, wine has been made in European countries. Since wine is made by fermenting grapes, it isn't affected by water. The United Kingdom which is island has similar water quality as Japan so it is popular to make whisky.
　Therefore, water difference deeply affects on food life and culture.

　Environment agency in Japan has researched about water environment and water resource in the nation, and it selected "best water" in 1985 to conserve water environment. For the background, Japanese water environment has had serious issue due to agricultural contamination, industrial wastewater, and chemical pollution in underground water by rapid economical development. Thus, in such situation, Japan decided to conserve water environment by selecting best water.

Ministry of the Environment ＨＰ

　Tap water is originally for people in the lack of water area to stably supply water. In countries such as Japan where has safe and delicious water environment, the time when it shifted into high gear to develop Tap water line was after the World War II so that it started only several ten years ago.
　On the rapid economical development, when residential zone had changed from urban central area to outlying cities, houses and factories were built near water source place. As a result, wastewater were discharged to water source and higher water purification methods and cleaner water source where is far from the area have been demanded.
　However, contamination toward such water source area has been progressing due to agricultural pollution, wastewater from industries, and harmful substance waste from factories. Therefore, more powerful treatment method and clean water place were demanded more and more.