A fundamental study on promotion of water use efficiency in Monobe river basin

Abstract

In the basin of Monobe river, one of the major rivers in Kochi prefecture in Japan, various environmental problems are becoming serious, and they cause decrease offish catches in the river. Among these problems, water shortage is a fundamental problem because it often worsens other problems such as muddy water and eutrophication.The ultimate goal of this study is, thus, to solve the water shortage problem in the river basin by improving efficiency of water use for agriculture sector, which consumes the largest volume of water in the whole sectors.Through interviews with various stakeholders, it is found that reducing water use amount for agriculture is accompanied by various difficulty and risks.First, daily water use fluctuates, and it is peaked in the weekend because the number of part-time farmers has been increasing. Yearly water use also jumps when each farmer switches the vegetable field into the rice paddy. Second, the rule of distributing water to each farmer is determined based on historical practices. Third, water use for agriculture sector has other functions of cultivating ground water and diluting wastewater discharged from each household. Fourth, most of farmers hardly feel necessity of improving efficiency of water use. Many residents are not aware of seriousness of the water shortage problem in the river either. Thus, reducing water use for agriculture would require not only farmers but also residents to cooperate each other to deal with the above difficulty and risks.It is difficult to build the above cooperation for a short time. In this paper, therefore, measures to cooperation and partnership among related parties are finally discussed from the viewpoints of project management.