盆地地下水流系统形成与影响因素分析

摘要

Constant head and flux boundaries are widely used upper boundaries of numerical simulations,which is however beyond the actual conditions.The differences between the two methods and their applicable conditions were compared in this study.Formation and controlling mechanisms of water table were discussed using an analytical method and an improved numerical simulation method of variable upper-boundaries was proposed.The formation and influencing factors of the northern Ordos Basin cretaceous groundwater flow systems was analyzed as a case study.The results show that water table of the northern Ordos Basin cretaceous flow systems was controlled by three factors including terrain,recharge conditions and hydraulic conductivity.Specific local climate,topography and aquifer lithology effect the development and evolution of groundwater flow systems by controlling water table.The numerical simulation method of variable flux upper-boundaries applied to analyze the impact of upper-boundaries changes on groundwater flow systems at basin scales is an effective way for deeply understanding the formation and evolution mechanisms of regional groundwater flow systems as well as for identifying the interaction between groundwater systems and climatic variations and vegetation changes.%目前区域(盆地)地下水流系统模拟研究中,常用的定水头与通量两种上边界条件刻画方法与实际条件存在差距.通过对比两种方法的差异和各自适用条件,采用解析法讨论地下水位的形成控制机制,提出了改进后的变通量上边界数值模型,并以鄂尔多斯盆地北部白垩系地下水流系统为例分析了盆地地下水流系统的形成与影响因素.研究表明,鄂尔多斯盆地北部白垩系水流系统地下水位受地形、补给条件和渗透系数三者共同控制,同时特有的气候、地形和岩性组合通过控制地下水位影响地下水流系统的发育演化.采用变通量上边界法探讨上边界条件改变对盆地水流系统的影响,对深刻认识区域地下水流系统形成演化机制,揭示地下水系统与上边界气候变化、植被生态变化之间的相互作用关系具有一定优势.