Intensive use of groundwater in some areas of China and Japan

In Japan and China, climate and landform are greatly different even in East Asia. The viewpoint of the groundwater flow system, which reflects climate and landform conditions, is required to compare groundwater in those regions. In Japan, where the average precipitation amount is 1,700 mm/yr and the distance from the mountains to the sea is less than 100 km, freshwater discharges as groundwater into the sea. In the China North Plain, where the distance from the mountains to the sea is more than 300 km and precipitation is about one third of that in Japan, it is not possible for freshwater to discharge directly into the sea, and its salinity rises even in the inland side from the coast and salt accumulation has generated. Those regions are economically important places and groundwater is utilised for various uses, such as domestic/business industrial and agricultural purposes. Due to heavy pumping in these areas, serious groundwater problems, such as the decline in the groundwater level, salt accumulation and land subsidence, have occurred. Those conditions are discussed in this chapter.