THE WATERWORKS OF TOKYO, JAPAN
Water was first brought into Tokyo from different sources by open canals, covered stone conduits and wooden pipes about 300 years ago, during the Togugawa Shogun Dynasty. The new system of water supply is all based upon the most approved foreign practice. The construction began in the fall of the year 1892, and the new water was first supplied in the fall of the year 1898. When the design of the new waterworks was made, the population of the city was about 1,200,000, and the water is provided for 1,500,000 at the maximum consumption of four cubic feet per person daily; but, with small additional works, the supply is supposed to be sufficient unt>I the population reaches 2,000,000. The water is taken from the Tama river about thirty miles from the city. The old canal used to supply the city with water is still in use from the intake at Hamura tc about two and one-half miles above the Yodobashi works. The latter part of the canal is 1 newly made one, and is lined with concrete slabs. The water of the Tama river is usually very clear and excellent; hut, when the heavy rains fall, it becomes quite muddy, and remains so a week or two after the rain. The area of the watershed is about 5,562,000,000 square feet, and is not much inhabited. The minimum discharge of the stream is about 200 cubic feet per second. There are three settling reservoirs, with a total capacity of 9,000,000 cubic feet, that is to say, thev can supply 1,500.000 people for thirty-six hours. These reservoirs are each 720 feet long by 360 feet wide, and the depth varies from nineteen feet to twenty feet, so that there is a bottom grade of one foot for clearing the mud deposited. The water from the new canal runs into them. The reservoir can be used either intermittently or continuously. When the heavy rain falls, the water becomes muddy, and the simple settlement is not satisfactory, so that last year (1904) alum was used for about thirty days. The water is brought from the settling reservoirs into filterbeds. There are altogether eighteen filterbeds, each of which is 258 feet long by 168 feet wide and nine feet deep. The total filtering area is about 780,000 square feet. The maximum rate of filtration is less than ten feet in twenty-fou: hours. The depth of sand is thirty inches and the gravel twenty-four inches. There is an automatic inlet regulator and an outlet weir gauge in each of the beds. There are arrangements to fill the beds with filtered water from their bottoms upwards. Clean water service reservoirs are at Yodobashi, Hongo and Shiba. The capacity of the above three reservoirs is exactly the same, namely, twelve hours’ capacity for 500,000 people, the w’hole city being divided into three equal portions. Each reservoir is divided into tw’O parts, and has a covering, to prevent dust from polluting the water and to keep out the sun’s rays. The water travels in a zigzag path, so as to give it a constant flow and no stagnation of water in the reservoirs. The whole city is divided into two districts, high and low. I he line of division is about twenty feet above the sea-level. The high district contains about one-third of the whole population, and the lowdistricts contain the remaining two-thirds. The water is delivered to the high district by pumps directly from the Yodobashi station; and for the lower parts of the city it flows by gravitation to the Shiba and Hongo reservoirs, whence it is distributed to the city by gravitation at present. There are four pumps at Yodobashi station, one of which is reserve. Each pump has a capacity of 1,000,000 cubic feet of wrater per twenty-four hours. The effective head is eighty feet to 100 feet above the ground, according to localities. There are twelve large Lancashire boilers and two sets of Green’s economisers. There are twelve different sizes of water pipes in use, from 1,100 millimetres to 100 millimetres in diameter, and the total length is 407 miles. The pipes were imported mostly from Belgium and Great Britain. Some of the smaller pipes and most of the specials have been made in Japan. There are 2,728 sluice-valves, large and small, 4,134 sunk fire hydrants. There are many air and safety – valves. The large sluice-valves, air-valves and safetyvalves were imported from abroad, while the small valves and fire hydrants were made in Japan. There are 235 district meters, which can be used also as fire hydrants. Water meters were all imported from America, England, Germany and France, and the total number in use at present is 20,556. All of the plumbing work is done by the city employes at the expense of the water consumers. The lead pipes have been made at Tokyo by a native firm, and the total amount of lead pipes used is 5,356 English tons. All the brass fittings have been made in Japan. The total cost of the works up to date is 8.260,936 yen ($4,130.468). City waterworks lionds at six per cent, interest were issued from time to time to raise the money. They are redeemable within thirty years from date of issue. The Imperial government made a grant of 2.942,000 yen ($1,471,000) to the whole works for the purpose of paying interest on bonds, and the above amount is given at the rate of 150,000 yen ($75,000) per year. Families using the new water are 139.000 in number, and there are also 20,529 meters for offices, hotels, factories, large families, laundries, etc. The total income of this year is expected to be 653,804 yen ($326,902), while the expenditure will be 198,988 yen ($99,494). The water charge for one faucet is five yen ($2.50) per year for a family with five persons, and for each extra person fifty sen (twenty-five cents) in addition a year. Each extra tap is charged three yen ($1.50) per year in addition. For a poor family taking water from street fountain the charge is 1.5 yen (seventy-five cents) per year. Water can be taken by meter, and the meters arc rented from the waterworks office. The rent varies from 2.40 yen ($1.20) per year for twelve millimetre diameter to 580 yen ($26.40) for one of 250-millimetre diameter. The charge for water by meters is seventy sen (thirty-five cents) for users of twenty cubic metres per month and three sen (one and one-half cents) for each extra cubic metre. For public baths the charge is two sen per cubic metre, and for sprinkling it is five sen (two and one-half cents) per cubic metre. I think the above charge is one of the cheapest in the world for the filtered water
•Paper read at the convention of the American Water* Works Association, 1906.
