Abstract
The results of forecasting domestic water demand in the long term are important for planning water supply facilities and operation and management systems. In Japan, recently, domestic water demand has been decreasing because of the progress of a water saving society such as spread of water-saving equipment. The trend methods has been used for forecasting water demand, however, water demand structures are complicated due to the variation of factors affecting them. It has therefore become difficult to forecast domestic water demand by the trend methods. Some waterworks have used multivariate analysis method using quantification method theory 1 for water demand forecasting. However, the method includes a issue not to be able to set in the changes of prescriptive factors in the future. The selection of explanatory variables is also a large issue. The aim of this study was to analyze changes of the prescriptive factors using quantification theory type 1 by the results of questionnaire surveys carried out at intervals and to reflect how far the water demand should be expressed on practical level focused on the selection of explanatory variables. As the results, changes of the factors and its contribution were revealed across the age. However, results of the water demand forecasting were not enough accurate because of the changes of factors. And, the considerations in water demand forecasting using multivariate analysis were mentioned.
