Rice Paddy Fields are Fresh-Water Resources. Today in Japan, the gross area of paddy fields has decreased. There were more than 3-million hectares in 1960, but they have been reduced by about 1 million. Consequently, 4-billion tons of fresh water have been lost. This is equivalent to the volume of water kept in 7 of the largest dams in Japan, containing 0.7 billion tons of water each.
Paddy fields are useful dams that store rain water in the rainy season.
It costs a huge sum of money to build 7 dams, and their construction may severely damage the surrounding environment. Paddy fields have been reduced under the pretext of production control. According to a trial calculation, more than 70 percent of farms in cities will be converted into housing sites. On the other hand, approximately 60 thousand hectares of farmland has been converted into housing sites. Hereafter, we need to consider paddy fields not only as production sites of rice but also as great dams in plain fields.