アンケート調査をもとにした都市の水需要構造分析-家庭用水を対象とする-

抄録

In the process of urban development, excessive concentration of population and industry causes water demand-supply gap, and areal potential of water supply cannot cover its deficit satisfactorily. Then, water demand has been an important subject of urban administration as many aimes at “smaller water demand city”.
For decreasing water demand at city level, two way of policies may be nominated as follows,
i) to decrease number of households and establishments,
ii) to decrease amount of personal water use.
The former needs re-examination of urban design such as land use and population planning, and the latter requires consideration of water use elastisity, i.e. how different ways of using takes what water amount difference in household and establishment level. In other words, the latter problem requires structure analysis for those level water demand system.
This study investigates the latter problem especially for domestic water demand. To analyze this matter, we make an assumption that personal water use is prescribed in outline by belonging type of household. That is to say, structure analysis means clarifications both the types of household and the personal water use patterns comprised in that type. In order to get household level data, we carried questionnaire survey out in A-city.
Going into details, our approach consists of following five steps,
1) making groups of factors which impact water use in household level,
2) extraction of representatives from factor groups,
3) pattern making with question-categories of representatives,
4) sample grouping with patterns, and
5) exammination of water amount in each sample group.
At the last step, we define the water use elastisity as difference of sample water amount in same group.
After emperical study in A-city, we found some results as below,
i) household members and possession of flush toilet are key factors in structuring types of household about water demand,
ii) comparing elastisities among groups, possession of flush toilet tends to lower water demand.
As these results imply directly, it may be sufficient for management of water demand system to inquire into a few factors. And a more important matter is that such factors are closely related to urban design, since factors are included in planning parameters. Then we are sure that our approach has a worth to extract such an important factor logically.