The city of Kumamoto and their surrounding area, where have the population over 0.7 million, are one of the unique prefecture capital because of its 100% groundwater supported city water. Recent expansion of the urban land-use area induces the decrease of groundwater resources in spite of economical water-use efforts, and the local government takes measures to maintain stable groundwater recharge rate. Also the groundwater contamination caused by the agricultural origin N-NO3 has been clearly rising recently. To maintain environmentally stable regional groundwater resources from both quantity and quality aspects, it is necessary to enlighten the people′s concern about the sustainable use of the regional groundwater resources. The report introduces the ongoing efforts conducted in the city of Kumamoto area for this purpose.
This study discusses a possibility of contribution of geography to water management in the Sanuki plain based on the field survey. The Sanuki plain is said to be one of the most water-scarce areas in Japan. The rapid increase in water demands due to the expansion of urban areas has influenced water allocation in agricultural sector. At the same time, it resulted in damages of the hydrological environment such as water pollution of river and irrigation pond. Thus, the water issues here are to construct the balanced water supply-demand system and to conserve the hydrological environment. There are three ways to keep the balance of supply and demand for the municipal water system: modification of supply, modification of demand, and doing nothing. The measures to modify the water supply are performed as follows: construction of multipurpose reservoirs, groundwater development, water transfer from the agricultural sector within the basin, inter-basin water transfer by constructing a dam in the upper part of the Yoshino river basin. The methods to modify demands are educational campaign emphasizing water conservation, and introduction of water-saving devices.
Although the large scale system of water supply has been built in the Sanuki plain, it is still difficult to supply adequate water during the dry period. Keeping the balance of supply and demand, requires the conjunctive use of surface water and groundwater, the conservation of hydrological environment, and the wise management of land use. The case study of the Miyako island provides effective information about conservation and management of groundwater in the basin as a hydrological unit.
A facilitator of the groundwater session of the Third World Water Forum commented that ‘Water is culture.′ Though water is a natural substance, it does not exist independently of humans because humans interact with nature. If we define culture as everything substantiated by human interaction, water is surely a part of culture. Nowadays a center of water issues is shifting from the realm of science to the realm of humans. Including environmental problems, issues that involve the value could not be treated by contemporary science based on Cartesian dualism. New science is necessitated, which would step into the problem of value. ‘Water is culture′ is raised here as an example to step into the problem of value in water issues.
Philosophical and social backgrounds of the “kyousei” (living together or symbiosis) concept were reviewed. Based on the review, we conclude that the most appropriate and useful perspective is commensalism rather than mutualism, coexistence, and parasitism, for discussing what relationship between human being and environmental water should be. The best condition of water or hydrological cycle cannot be determined scientifically. Therefore, we have to decide a desirable one by mutual consent among the interested stakeholders and to sustain the condition without failure from various points of view. In the process of decision making, hydrology is required to play the following roles: 1) to provide correct and scientific knowledge by making a diagnosis of actual water environment, 2) to suggest and organize the desirable relationship between human being and water through discussion from aspect of Fuudo, and 3) to help sustainable water management in reasonable way to evaluate gains and losses for each stakeholder.