Amounts of Water Needs in the Volcanic Island of Oshima, Izu

Abstract

The author has studied the problem of how many people can live at the present state of water supply dependent mainly upon rain water in the volcanic island of Oshima. In this island, all the precipitated water upon roofs of rural houses is collected into the Avater tanks of each house. Inve-stigations of amounts of water necessary for rural houses were done at Moto-mura, Nomashi and Habu-no-minato village The results are as follows; 1) The relation between the number of people and the amount of water needed by families at each village is expressed in the following experimental formula. Y=AXb Y signifies amount of water needs, X means numberr of people in a family, and A and b are constant values. At several villages, he obtained the following values. Moto-mura Y=69X0.5 Nomashi Y=52X0.5 Habu-no-minat o Y=39X0.5 2) The increasing coefficient of water needs of rural families was equal to each other or all villages, but basic amounts of water needs (A) showedd dillerent values. The value of A was the biggest at the most humid village, and tine smallest at the most arid one in the island. 3) Using the former formula, he calculated total amounts of water needs at all rural families in Oshinia island underr the present conditions, and he estimated the total amount of water needs by cattle, ships, factories, hotels, etc.. Adding these two values, mentioned above he found the total amount of water needs in Oshima. This value is only 0.016% of rain water on Oshima island.