Using temperature depth profiles to identify the origin of groundwater salinization in Pingtung coastal plain, Southern Taiwan

Temperature depth profiles has been applied on many topics, e.g. climate change, groundwater velocity and saltwater-groundwater interface. In this study, temperature depth profiles are used to identify the origin of groundwater salinization in Pingtung coastal plain, southern Taiwan. Some monitoring wells in the coastal area have reached salty groundwater. Even some of the deeper aquifers, down to 300 m are saltwater. There are two arguments for the origin of those saltwater. One theory is those saltwater were Holocene transgression relics. The other theory is that those saltwater were sea water intrusion due to over-pumping of groundwater. Using the measured temperature depth profiles, a 2D numerical model is developed to simulate the heat transfer of sea water intrusion. The preliminary results show that the cause of salinization is not likely by the modern sea water intrusion. The sea water below a depth of 100 m is a cooler source and the intrusion of sea water should decrease temperature in aquifer. However, the measured temperature data of those salty aquifer are higher.