Study On Groundwater Table Control And Management In Representation Areas Of China

Groundwater resource is abundant in China, and it plays an important role in water resources in this nation. In recent years, due to unreasonable exploitation and weakly management of groundwater, a series of ecological and geological environmental problems have occurred. These problems are related to the changing of groundwater table directly or indirectly. Therefore, studying on the control and management of groundwater table has great significance in the control and improvement of groundwater environment.The variation of groundwater table is the main manifestation of groundwater resources amount, and it is also the most important control indicator. Based on the analysis of the status of groundwater development and utilization of China and the corresponding ecological and geological environmental problems, the suitable groundwater table and the critical groundwater table are put forward as the groundwater control and management index. Control and management of groundwater table in North China plain, the northwest inland and coastal areas are researched from points to area, from the partial to the whole by the method of combination of theoretical analysis with practical achievements as well as regional macro analysis with deep analysis of representative area.(1)In North China Plain, the relation between environmental problems and groundwater table has been analyzed, and the corresponding suitable groundwater table and critical groundwater table have been given in view of the status of groundwater development and utilization as well as its influences on groundwater environment. In the piedmont alluvial plain, the suitable groundwater depth for regulating functions is 10m, and the critical groundwater table is the water table that annual average overdraft coefficient is 0.3 or serious overdraft groundwater table in other methods. In the middle-eastern plain, the suitable groundwater depth on shallow aquifer that prevents the soil salinification is 2~3m, and that prevents the ground fissure is 7m; the suitable groundwater depth of confined aquifer that avoids the broad area land subsidence is 50m.In the karst collapse district, the suitable groundwater table should be above the top of karst aquifer (2m). In the city refuse disposal areas, the suitable groundwater table should be 1m below the bottom of refuse landfill.(2)In the northwest inland, the relation between ecological problems and groundwater table has been studied, in view of the status of groundwater development and utilization as well as the existing ecological environmental problems. The suitable groundwater depth in natural plant community that prevents nature vegetation decline is 2.0(2.5) ~4.0(4.5)m. The suitable groundwater depth in artificial oasis that prevents the soil salinification is 1.2~1.5m in irrigation time, 1.3~1.5m in defrosting time and 2.2~2.7m in frozen time.(3)In coastal areas, seawater intrusion is put forward, and through analysis of the relation between groundwater table and the content of Cl-, the suitable groundwater table to prevent the seawater intrusion is -5~-6m in the center head of groundwater depression cone and the critical groundwater table is -8m.Based on the above analysis, the target, principle and methods of total quantity control of groundwater withdrawal,are analysed based on the groundwater table control. To deal with problems of water resources management in China, the requirements and recommendations for the implementation and supervision of groundwater table management are put forward.These will have important practical significance in scientific management of groundwater resources and the realization of the water resources sustainable utilization in our country.