黄河流域の地下水研究

Abstract

The Yellow River is a big river, 5,464 km long, and its basin has a catchment area of 795,000 km2 including a closed inland catchment area. One of the four prehistoric civilizations of the world developed in this basin. Following the Yellow River civilization, most dynasties that ruled major parts of China were located in or around the Yellow River basin. From ancient times the Yellow River has been the mother river of China, as all of the Chinese people agree. A five-year project to understand the whole picture of the groundwater of the Yellow River basin was started in 2002, which was called the Yellow River Groundwater Project. This was part of a larger project called Research Revolution 2002 (RR2002) under the auspices of the Ministry of Education, Culture, Sports, Science and Technology, Japan. As the Yellow River basin was a major research field, research activities were carried out with close cooperation among Geological Survey of Japan and China Geological Survey, and several universities and related institutions of the two countries. The Yellow river basin extends in EW and the difference in elevation between headwater and river mouth is about 5,000 m. At the headwater there are small glaciers and permafrost areas. In the Yellow River Groundwater Project, surveys and observations of permafrost were carried out at the headwater area. Hydrologic surveys of groundwater and surface water were conducted throughout the basin, and collected water samples were analyzed for general quality and oxygen and hydrogen isotope ratio. As knowledge of rocks and formations containing groundwater is very important, information concerning geology, especially the thickness of aquifers and locations of faults was carefully examined. The final target of the project was reconstruction of past groundwater by developing a groundwater circulation model of the vast Yellow River basin, taking account of all data collected, and predicting the future from the model thus constructed. The model we developed is a three-dimensional groundwater circulation model covering an area of about 1.6 million km2. Simulation results, for example on the North China Plain, show an extreme lowering of the deep groundwater head after twenty years if groundwater is extracted with the same pumping trend as at present.