Trends of groundwater data from the Korean National Groundwater Monitoring Stations: indication of any change?

Widespread climate change can impact on groundwater conditions. We evaluated the groundwater data for 1996-2008 obtained from the National Groundwater Monitoring Stations (NGMS), in the context of the global warming effect. Indications of air temperature and sea level rises were evident in the period. The groundwater levels were generally decreasing and most of this decrease was attributed to increased pumping nationwide, but no indication for any effect of sea level rise on groundwater level in coastal aquifers was found. The electrical conductivity (EC) values of groundwaters were very high in metropolitan and industrial areas, which were indicative of anthropogenic groundwater contamination and progressive groundwater quality deterioration. A systematic EC rise in coastal groundwaters, as a possible result of the sea level rise, was not observed. The groundwater temperature variation was the most striking. The majority of the monitored shallow and deep groundwaters exhibited increasing trends at mean rates of 0.04-0.09 °C/yr. The widespread and prevailing increase in groundwater temperature nationwide, with increasing air temperature, is strongly indicative of the effect of global warming. The increasing trend became more distinctive every year. However, these significant conclusions require further groundwater monitoring and re-evaluation. [ABSTRACT FROM AUTHOR]