Deterioration of groundwater quality in the coastal Pingtung Plain, southern Taiwan

Population growth, urban expansion and economic development have persistently raised the demand for water supply and consequently, greatly increased the exploitation of groundwaters in the Pingtung Plain of southern Taiwan over past decades. Over-pumping of groundwaters, due to booming freshwater aquaculture and agricultural activity, has caused the groundwater level to fall and land to subside below sea level in some coastal areas. Isotopic and chemical groundwater analysis has verified the deterioration in coastal groundwater quality, due to active seawater intrusion through the offshore outcrops of both unconfined and confined aquifers, since 1980, The greatest extent of seawater encroachment has been estimated to be as far as 8.5 km inland with an affected area of about 104 km(2) for the deep confined aquifer in 1996. Remedial measures need to be immediately enforced to effectively restrain sea water encroachment and to alleviate groundwater salinization.