地下水管理における政府の役割―バンコクの地盤沈下問題を事例に―

Abstract

Land subsidence is a common intermittent problem in Asian Megacities, such as Tokyo, Osaka and Bangkok, of different economic development stages. The purpose of this paper is to justify government intervention and clarify policy options against land subsidence problem with Bangkok case. First of all, government intervention is necessary because land subsidence problem can be regarded as an example of collective action problems that are hard to be solved by voluntary cooperation of stakeholders. Especially in case of Bangkok, such cooperation was prevented due to factors including group size, subsidence rate and high cost of waterworks construction. The roles government played in mitigating land subsidence problem in Bangkok can be classified as follows; (1)enacting groundwater law that requires groundwater users to get a pumping permission from government, (2)establishing areas, based on monitoring data, where groundwater pumping is strictly regulated, (3)introducing groundwater fee system to give people disincentive to use groundwater, (4)construction of waterworks. In sum, land subsidence in Bangkok was mitigated by policies that fostered conversion of water supply from groundwater to surface water, which was made possible by not only regulating groundwater pumping but also providing