Chemical and Physical Evidences in the Groundwater Aquifer Caused by Over-Pumping of Groundwater and Their Countermeasures in the Major Asian Coastal Cities

Abstract

Economic growth of urban area induces the huge water demand for the city production and this creates the groundwater related disasters in many Asian cities. This situation has started from 1960s to 1970s Japan. After, many coastal cities in South East Asia had experienced similar problems later 1980s–2000s. This was caused by over-pumping of groundwater in the urban area and the related local city governments had tried to make countermeasures to protect such groundwater disasters by adapting the groundwater pumping regulation with the help of their national government. In the case of Japan, it has good success and the dropped groundwater level has clearly recovered by the help of the worm humid hydrological condition of Japanese island. Similar recovery has confirmed in Taipei and Bangkok, but it has not yet succeeded at Jakarta.

At the planning stage of the present project, we believe that those groundwater over-pumping situations must create the forced groundwater flow in the related aquifer and the chemical information on the environmental change of those urban areas should be remained as the precise time series information along the groundwater flow line in that aquifer like the paleo-hydrology record in aquifer. For this particular purpose, we have developed the young age tracer of groundwater such as CFCs and ⁸⁵Kr for the recent 100 years historical data analysis. However, we have confirmed that it could not use CFCs age tracer in the urban aquifers because of man-made local CFCs contamination especially dominated at urban area. Instead, we showed that the CFCs contents at urban area can be useful to understand the induced relatively young vertical flow flux through shallower aquifers caused by the man made depressed groundwater potential under the city area. This kind of situation has been confirmed at Tokyo, Bangkok and Jakarta area and these vertical induced fluxes are much more than the natural lateral groundwater flow along the aquifer. The 3D groundwater flow simulation clearly showed this kind of induced vertical flux (‘induced recharge’) dominated at the groundwater depression area where was created by the over-pumping of the groundwater resources in city area.

In spite of these severe situations, our comparative study clearly shows that the potentiality of the positive groundwater recharge in the coastal Asian city aquifer. It works effectively to recover the depressed groundwater level, if the groundwater pumping regulation works perfectly with the help of infrastructure construction of the additional surface water supply system and the steady legal system for the groundwater resources.