Hayashi Takeshi, Tokunaga Tomochika, Aichi Masaatsu, Shimada Jun, Taniguchi Makoto
Akita University, Japan.
Sci Total Environ. 2009 Apr 15;407(9):3165-72. doi: 10.1016/j.scitotenv.2008.07.012. Epub 2008 Sep 26.
The Kanto plain that is the largest depositional plain in Japan has the largest urbanized area called Tokyo Metropolitan Area. This plain has experienced extensive groundwater withdrawals for water resources and human induced disasters such as land subsidence in the process of urbanization. Japanese national government and local governments have monitored groundwater levels and settlement of ground surface for about half a century. These data are useful not only for the prevention of these disasters but for the evaluation of the change of groundwater flow beneath the urbanized area. However, few hydrological and hydrogeological studies about the change of groundwater flow in this plain have been conducted until now except for several studies which were limited in areal extent. In this paper, changes of the distribution of hydraulic heads in the central part of this plain are discussed using the long-term groundwater level observation data to evaluate the change of groundwater flow. The temporal changes in the distribution of hydraulic heads in a major confined aquifer (the second aquifer) and the areal extent of the urbanized area for approximately 50 years can be summarized as follows. In the latter half of the 1950s, urban area was limited in the southern region of the study area and hydraulic head gradually declined from the northwest to the southeast in the study area. After the 1960s, urban area extended toward the north and groundwater in the northern part was largely abstracted until the 1980s. As a result, hydraulic heads in this area markedly declined. On the other hand, hydraulic heads in the southern part began to rise because of the restriction of groundwater withdrawals. In recent years, low hydraulic head area has been formed from the northern region to the central region. These results suggest that the groundwater flow which was affected by urbanization (groundwater withdrawals) has continued to change over several decades, even after the regulation of withdrawals, and hence, the continued monitoring of the groundwater environment is important for the sustainable use of groundwater resources.
关东平原是日本最大的沉积平原，拥有名为东京都市区的最大城市化区域。在城市化进程中，这片平原经历了为获取水资源而大量抽取地下水以及地面沉降等人为诱发灾害。日本国家政府和地方政府已经对地下水位和地表沉降进行了约半个世纪的监测。这些数据不仅对预防这些灾害有用，而且对评估城市化区域下方地下水流的变化也很有用。然而，到目前为止，除了一些范围有限的研究外，关于这片平原地下水流变化的水文和水文地质研究很少。本文利用长期地下水位观测数据讨论了该平原中部水力水头分布的变化，以评估地下水流的变化。一个主要承压含水层（第二含水层）中水力水头分布的时间变化以及大约50年的城市化区域范围可总结如下。20世纪50年代后半期，研究区域南部的城市区域有限，研究区域内水力水头从西北向东南逐渐下降。20世纪60年代以后，城市区域向北扩展，直到20世纪80年代，北部的地下水被大量抽取。结果，该区域的水力水头显著下降。另一方面，由于地下水抽取受到限制，南部的水力水头开始上升。近年来，从北部地区到中部地区形成了低水力水头区域。这些结果表明，受城市化（地下水抽取）影响的地下水流在几十年间持续变化，即使在抽取受到管制之后也是如此，因此，持续监测地下水环境对于地下水资源的可持续利用至关重要。
