基于TOUGH2的柴达木盆地诺木洪剖面地下水流模拟

Application of TOUGH2 in groundwater numerical simulation of Qaidam Basin

基于TOUGH2数值模拟软件的EOS9模块建立柴达木盆地典型剖面饱和-非饱和地下水流数值模型。模型中对上边界条件的处理采用考虑潜在蒸发能力和土壤含水率的表土含水量计算方法。利用试估校正法对模型参数进行识别验证,模拟结果得出实测水位与模拟水位拟合相关系数为0.976 4;均衡计算结果表明地下水补给量主要为南侧山前补给,占补给总量的90.1%,排泄量主要为溢出排泄和蒸发排泄,分别占64.3%和35.7%。地下水流系统发育三级流动层次,其中局部水流系统排泄是地下水排泄的主要方式,循环量主要为泉溢出排泄,占58.8%;中间流循环量主要为溢出排泄和蒸发排泄,占27.6%;区域流循环量主要为蒸发排泄,占13.6%。

In order to accurately and efficiently study the transforming relationship between surface water and groundwater, and the renewal capacity of groundwater system in Qaidam Basin, northwest China, a two-dimensional variably saturated numerical model of a typical profile from Nuomuhong River to Amunike Mountain was developed using TOUGH2 simulator. On the basis of previous studies, the evaporation was a function of soil saturation given as an upper boundary to characterize water transport near surface through iterative calculation. The numerical model was calibrated with 41 groundwater observation data based on trial-and-error method. The simulated results fitted well with observation data. The correlation coefficient of simulated groundwater heads was 0.9764 m, and the absolute error was 1.6 m. The simulation results showed that the typical profile of Qaidam Basin could be divided into three orders of groundwater flow system：local groundwater flow system accounted for 58.8% of total amount of groundwater flow with spring as the main discharge; the middle flow system accounted for 27.6% of the total amount of water, with evaporation and river as the main discharge; regional flow system accounted for 13.6% of total amount of water, with evaporation as the most important discharge. The results showed that TOUGH2 with modified boundary condition can accurately describe water transport in variable saturated zone under the conditions of phreatic fluctuation. The study of the renewal capacity of groundwater and the characteristic of groundwater flow system has great significance for the areas lack of intensive studies. In the future research, different supply sources and forms, as well as dispersion and density changes can be taken into consideration to simulate groundwater ages and further study the groundwater systems.