Characterization of the regional groundwater quality evolution in the North Plain of Jiangsu Province, China

Groundwater plays an important role as domestic water in the North Plain of Jiangsu Province, China with a total area of 6.37 × 104 km2. The characterization and evolution of regional groundwater quality were surveyed and discussed based on the field data, including 597 data collected in the 1980s and 1346 samples analyzed in the 2000s. The evolution of groundwater quality for phreatic, shallow and deep confined aquifers for more than two decades was discussed by comparing the distribution maps of TDS concentration and groundwater hydrochemical facies in different periods. Piper diagrams of water chemical composition showed that there were significant changes for the groundwater quality during the past 20 years, which is mainly attributed to two opposite effects from human activities. On the one hand, agricultural irrigation using the fresh surface water and exploration of the saline groundwater for domestic and industry usage lead to the desalination of groundwater in large-scale areas. On the other hand, groundwater pollution including human waste and heavy use of fertilizers lead to the deterioration of groundwater quality in local areas (e.g., the increase of TDS concentration is an obvious indicator). It is suggested that the groundwater, especially the shallow phreatic water, could be artificially diluted by groundwater exploration and usage, which may provide an important water source to make up for the serious shortage of living water in this study area. However, groundwater pollution such as from nitrogen needs to be controlled as a critical issue to be faced in the next step.