Project Summary

This project assessed the effects of human activities on the urban subsurface environment, an important aspect of human life in the present and future but not yet evaluated.  This is especially true in Asian coastal cities where population numbers and density have expanded rapidly and uses of subsurface environment have increased.  The goal of this project is to evaluate the relationships between the development stage of cities and various subsurface environmental problems, including extreme subsidence, groundwater contamination, and subsurface thermal anomalies.  We address the sustainable use of groundwater and subsurface environments to provide for better future development and human well-being.

Most global environmental studies have long been focused on the environmental issues above ground surface such as air pollution, global warming, seawater pollution, and decrease in biodiversity.  Subsurface environmental issues are also important for human life in the present and future, but have been largely ignored because of the invisibility of the phenomena and difficulty of the evaluations. Subsurface environmental problems such as subsidence due to excessive pumping, groundwater contamination, have occurred repeatedly in Asian major cities with a time lag depending on the development stage of urbanization.  Therefore, we may be able to assess future scenarios if we can evaluate the relationships between subsurface environmental problems and the development stage of the city.

This project deals with; (1) Relationships between the development stages of the cities and subsurface environmental problems are assessed by socio-economical analyses and reconstructions of urban areas by uses of historical records; (2) Serious problems in subsurface environments and changes in reliable water resources are studied after evaluations of groundwater flow systems and changes in groundwater storage by uses of hydrogeochemical data and in-situ/satellite-GRACE gravity data; (3) We also evaluated accumulations of the materials (contaminants) in subsurface and their transports from land to ocean including groundwater pathways by uses of chemical analyses of subsurface waters, sediments and tracers; and (4) Subsurface thermal contamination due to the “heat island” effect in urban areas are evaluated by reconstruction of surface temperature history and urban meteorological analyses.

This project deals with “Subsurface environmental problems” by interdisciplinary approaches with water, material, and heat transports beyond the boundaries between surface-subsurface and land-ocean. This project shows that the subsurface environment is a hidden-circulated system linked with atmosphere, ocean, and human, by reconstructions of the last 100 years history of subsurface environment. The subsurface environment is evaluated as adaptation, alternative and resilience to the global changes, by two indices; changing climate and society, and natural capacity. This project finally suggests the wise use and management of subsurface environment for future development and human well-being.

Project Leader, Makoto Taniguchi