GroMoPo Metadata for Madison Aquifer Karst MODFLOW model

Karst aquifers exhibit a dual flow system characterized by interacting conduit and matrix domains. This study evaluated the coupled continuum pipe-flow framework for modeling karst groundwater flow in the Madison aquifer of western South Dakota (USA). Coupled conduit and matrix flow was simulated within a regional finite-difference model over a 10-year transient period. An existing equivalent porous medium (EPM) model was modified to include major conduit networks whose locations were constrained by dye-tracing data and environmental tracer analysis. Model calibration data included measured hydraulic heads at observation wells and estimates of discharge at four karst springs. Relative to the EPM model, the match to observation well hydraulic heads was substantially improved with the addition of conduits. The inclusion of conduit flow allowed for a simpler hydraulic conductivity distribution in the matrix continuum. Two of the high-conductivity zones in the EPM model, which were required to indirectly simulate the effects of conduits, were eliminated from the new model. This work demonstrates the utility of the coupled continuum pipe-flow method and illustrates how karst aquifer model parameterization is dependent on the physical processes that are simulated.喀斯特含水层（Karst Aquifer）呈现出兼具管道域与基质域相互作用的双重水流系统特征。本研究针对美国南达科他州西部麦迪逊含水层的喀斯特地下水流动模拟，评估了耦合连续体管道流（Coupled Continuum Pipe-Flow）框架的适用性。研究在为期10年的瞬态模拟时段内，依托区域有限差分模型模拟了耦合管道-基质水流过程。本研究对现有等效多孔介质（Equivalent Porous Medium, EPM）模型进行修正，纳入了主要管道网络，其空间位置由染料示踪数据与环境示踪剂分析结果约束。模型校准数据涵盖观测井实测水头数据与四处喀斯特泉的流量估算值。相较于原始EPM模型，新增管道模块后，模型对观测井水头的拟合精度得到显著提升。引入管道水流过程后，基质连续体的水力传导率分布可更为简化。原EPM模型中为间接模拟管道效应而设置的两处高导水区，在新模型中被移除。本研究验证了耦合连续体管道流方法的实用性，并阐明了喀斯特含水层模型的参数化方案如何依赖于所模拟的物理过程。