Coupled Modeling Of Salt Movement And GroundwaterFlow In Inland Basin

The inland basins are mainly distributed in the arid and semi-arid regions of China. Groundwater resources in these regions is not only the precious resource supporting the economic and social development, but also is an important factor maintaining ecological balance. And it is cannot be ignored that improper utilization of groundwater may cause some environment problems. The inland basins in China, with scare precipitation and intensive evaporation, have long suffered from water shortages, particularly from a scarcity of clean water. The conversion between surface water and groundwater is frequently. Consequently, a clear understanding of groundwater flow system is critical for solving these problems.The theory of groundwater flow system has become one of the most important tools in the study of modern hydrogeology. However, most researchers tend to focus on the properties of the aquifer, while ignoring the effects of properties of fluid on groundwater seepage when they use this theory to solve hydrogeology problem. Particularly in the inland basins, the difference in the chemical components of groundwater should arise more attention.By modifying a reactive transport model, the author developed a variable density flow numerical model with the capacity of completely coupled modelling of flow and solute transport. After analysis of the characteristics of hydrogeology and the water cycle, an ideal profile of inland basin is formed and simulated using the modified code. According to the simulation result, groundwater are divided into different flow systems by streamline method and age method. The quantitative analysis of the effects of the fluid density on groundwater flow system and water cycle also is presented. In addition, based on the hydrodynamic method, the inhibition mechanism of regional flow system are discussed in this dissertation, as well as the inhibition degree of fluid density on regional flow system.The simulation results of the ideal profile show that the groundwater can be divided into three different flow systems. The effects of fluid density on groundwater systems are very significant. With the increase of chemical component concentration in the central basin, regional flow system is restrained and local flow system is enhanced. When the TDS of central basin increased to 40 g/L, the water circulation proportion of regional system will decrease 45.43%, while that of local system will increase 39.28%. The calculation results of inhibition degree show that the regional flow system may disappear when the TDS increase to critical concentration because the total potential energy in the piedmont will not be enough to drive water flow to central basin by deep circulation.Finally, the groundwater flow system of a typical profile in Qaidam basin is studied. Under present situation, only two orders of flow system are developed in the typical profile, i.e. regional flow system and local flow system. And the proportion of local flow system is up to 82.25%. Combined with the ancient climate fluctuations, the salt movement process and evolution in geological history is reproduced. The salt movement is significant controlled by the water flow system. In addition, there is a tendency that the chemical component will continue to concentrate.