The Dynamics and Evolution of a Coastal Water-Table Aquifer Under a Regime of Slowly Rising Sea Level

该项目解决了南卡罗来纳州森林-沼泽边界地下水中淡水-咸水界面的动态和演变问题。这一界面的位置和表现(即清晰度与扩散度)受短期强迫(日潮、日ET周期和降雨事件)、阶段性风暴潮和长期海平面上升的影响。对陆地上释放的污染物的去向及其对邻近沼泽的影响的预测，取决于对这一界面及其附近地下水运动的清楚和定量的了解。由于复杂的作用力和边界条件，现有的沿海含水层模型过于简单，无法充分模拟这种系统。此外，没有足够的水头和盐度现场测量来测试可能使用的复杂数值模式。作为对这一问题的补救办法，该项目的目标是收集森林-沼泽边界沿线的头部和盐度的长期测量数据，并利用这些数据开发、校准和验证该系统的数值模型。沿每个横断面的空间密集的压力计网络将配备记录压力传感器(在室内组装)，这些传感器将收集关于短期强迫的影响的数据。根据地貌和地层标准以及在高沼泽土壤中发现的树根的C-14测年，将选择横断面来代表在海平面上升的情况下，森林覆盖的更新世海滩山脊地形转变为全新世盐沼的各个阶段。这将提供一个独特的机会，用真正的长期数据来检验我们的数值模型。该项目的结果可供管理机构用于环境影响评估和规划，也可供对森林和沼泽生态系统之间相互作用感兴趣的生态学家使用。

This project addresses the problem of the dynamics and evolution of the freshwater - saltwater interface in ground water along the forest - marsh boundary in South Carolina. The position and expression (i.e. clarity versus diffuseness) of this interface is governed by short-term forcings (diurnal tides, daily ET cycles and rain events), episodic storm surges and long-term sea level rise. Prediction of the fate of contaminants released on land and their impact on adjacent marshes depends on a clear and quantitative understanding of the movement of ground water at and near this interface. Because of the complex forcings and boundary conditions, presently available models for coastal aquifers are too simple to adequately simulate such systems. In addition, adequate field measurements of head and salinity are not available to test complex numerical models that might be used. As a remedy to this problem, the objectives of this project are to collect long-term measurements of head and salinity along transects across the forest-marsh boundary and to use the data to develop, calibrate and validate a numerical model of the system. A spatially dense network of piezometer along each transect will be equipped with recording pressure transducers (assembled in house) that will gather data on the effects of short-term forcing. Based on geomorphic and stratigraphic criteria and C-14 dating of tree roots found in high marsh soils, transects will be selected to represent stages in the conversion of a forested, pleistocene beach ridge terrain into a Holocene salt marsh under a regime of rising sea level. This will provide a unique opportunity to test our numerical model against truly long-term data. The results of this project could be used by regulatory agencies for environmental impact assessment and planning and by ecologists interested in interactions between forest and marsh ecosystems.