Study of Methods for Estimation of Water Resources Development Stages

抄録

Recently water shortages in Japan's principal river systems have been occurring as a constant and frequent phenomenon, creating a very serious social problem. It is probable that there will be increased water consumption in the future. At the same time water resources development is becoming increasingly difficult to undertake because suitable sites for new dams are being exhausted. It is all but certain, therefore, that there will be further tightening of the water supply situation.
Given the aforementioned situation, this paper analyzes water resources development stages in Japan mainly since the Meiji Restoration (1868). Water resources development has progressed through three stages, analyzed from the perspective of development costs. These stages include (1) a period of zero development costs; (2) a period of slowly increasing development costs; (3) a period of rapidly rising develoment costs. In fact, the rise in water development costs in Japan. has been caused generally by the expansion of cities rather than the growth of agriculture. Expansion of river water use is evident in certain rivers in the period of rapidly rising development costs.
Useful for water development planning is the careful evaluation of historical trends in development costs. But it is difficult to estimate further trends in development costs directly. Therefore, we suggest an indirect method of estimation by means of a “Q-V curve, ” where the trend of water development costs can be considered in relationship to Q-V (Q: developed water*, V: required capacity of reservoir).
The “Q-V curve” is the so-called stock-type hydrological index, and it offers abundant information about water development in river systems. A computer simulation of the Q-V curve in the Yahagi River basin is given as an example in this paper.