Review of Groundwater Management and Land Subsidence in Bangkok, Thailand

Abstract

The history of groundwater use in Bangkok started in 1907. Since then, groundwater is the important source of public water supply concurrent with surface water. Both public and private sectors had freely developed groundwater for several decades before consequent affect revealed. Due to the past uncontrolled over pumping of groundwater, certain aquifers and overlying clay layer are under substantial stress, leading to serious land subsidence which at its most severe amounts to 10 cm/year (1978–1981). In certain places, with combined surface loading, this has amounted to a maximum recorded settlement of 100 cm over a 21-year period (1978–1999) and groundwater level has declined to 55 m from ground surface. The increasing of groundwater abstraction reached it maximum at 2.2 million cubic meters per day (Mm³/d) in 1999. The mitigation actions have been required if they are to be reinstated and stabilized. The subsequent strict mitigations such as declaration of “Groundwater Critical Zone” covered large area totally seven provinces including Bangkok. The mitigation included reducing the permissible usage of registered wells, promoting public awareness in groundwater conservation, and finally implementing “No permission for groundwater development in public water ­supply service area” in the Bangkok metropolis. In addition, Groundwater Tariff and Groundwater Conservation Tax have been implemented. All these mitigations have been determined to control the total abstraction to meet permissible yield which has been studied at 1.25 Mm³/d. The strict mitigations finally return good result.