Groundwater Management in a Land Subsidence Area

Abstract

In a stressed hydrological environment, the practice of groundwater management is important for sustainable water use. Land subsidence in the Nobi Plain in the central part of Japan has produced the largest sea-level zone in Japan. A good correlation is found between volume of land subsidence and groundwater withdrawal, and the regression line indicates the value of the optimum amount of groundwater withdrawal at which the volume of land subsidence becomes zero. The artesian head of confined groundwater in Japan began to increase over the first half of the 1980s as a consequence of both the regulation of groundwater withdrawal and water economisation. The unexpected rise in groundwater level has resulted in a buoyancy of underground structures. In contrast to the past state of affairs, lowering the groundwater level as economically as possible is now a pressing matter in the greater metropolitan area. As a result of groundwater conveyance into polluted surface waters since the latter half of the 1990s, the effect of an improvement in water quality has become apparent. Comparison of the pre- and post-urbanisation state reveals a decrease in the rate of groundwater recharge owing to an enlargement of the impervious land area. It is worthy of special mention that coactions between local people, enterprises and administrative offices have fulfilled their function in terms of enhancing proper management and preserving a better environment for groundwater. An administrative body has also driven forward the actual enforcement of policy concerning the conservation of groundwater resources and the establishment of a symbiotic water environment.