Abstract
Population of Muroran city has been decreased since 1967. This study firstly reproduced actual water supply and demand during 1960 to 2006. Water demand of life per day increased 7,733 cubic meters in 1960 into 18,217 in 2006. Water demand of life per capita increased 49 liters in 1960 into 186 liters in 2006. The study secondly estimated detail of water demand of life. Muroran has three water purification plants. The study thirdly makes effects of Chiribetsu stopping water supply in 2007 clear. The sufficient capacity of Chitose recoveries the reduction of water supply by the pause of Chiribetsu.