Collaborative Research: Mechanisms Producing Variation in Lake Salinity in Dune Environments: Nebraska Sand Hills

沙山含水层系统拥有数百个浅湖，盐度从淡水到超过100克/升不等。迄今为止，人们对产生和维持这些大盐度梯度的机制知之甚少。在这项研究中，我们计划确定在整个沙山含水层系统中观测到的湖泊盐度的时空变化是否由于：1)地下水流入/流出与湖泊蒸发的比例差异，或2)本地和区域尺度地下水流动系统向湖泊输送溶质的空间变化。为了测试这些不同的湖泊盐碱化端元假设，我们将为我们的研究区域开发详细的变密度地下水流动、溶质运输和地表水-地下水相互作用的三维模型。这些模型将使用新的地球物理（EM， MR， TDEM）调查进行测试。我们还将收集湖水和地下水的水力、地球化学和同位素样本，以表征近湖含水层的地表/地下溶质分布。我们将利用硅藻和光激发发光方法评估湖泊盐度的时间趋势。这项研究将改进地下盐度检测方法，并更好地了解大规模环境灾害(如海啸（2005年印度尼西亚和孟加拉国）和飓风（2005年美国密西西比州和路易斯安那州）造成的大量致密含盐流体沉积在浅层淡水含水层上的后果。这些基于物理的模型也可能适用于其他地区的沙丘湖系统，在这些地区，沙丘湖系统在当地水文和水资源中起着重要作用（例如，中国、尼日尔、澳大利亚）。该项目将支持来自内布拉斯加州大学、印第安纳大学和俄克拉荷马州立大学的一些本科生和研究生。此外，我们将直接涉及人口密度低于每平方公里1人的内布拉斯加州西部的K-12学生和教师，该研究将汇集来自澳大利亚和北美的水文学家、地球物理学家和湖泊学家。

0609579PersonThe Sand Hills aquifer system hosts hundreds of shallow lakes having salinity levels ranging from fresh water to more than 100 g/L. To date, the mechanisms responsible for generating and maintaining these large salinity gradients are poorly understood. In this study, we plan to determine whether or not the spatial and temporal variations in lake salinities observed across the Sand Hills aquifer system are due to: 1) differences in the ratio of groundwater inflow/outflow to lake evaporation or 2) spatial variations in delivery of solutes to lakes from local- and regional-scale groundwater flow systems. In order to test these different end-member hypotheses of lake salinization, we will develop detailed three-dimensional models of variable-density groundwater flow, solute transport, and surface water-groundwater interactions for our study area. The models will be tested using new geophysical (EM, MR, TDEM) surveys. We will also collect hydraulic, geochemical, and isotopic samples of lake water and groundwater in order to characterize the surface/subsurface solute distribution in the near-lake aquifer zone. We will evaluate temporal trends in lake salinity using diatoms and optically-stimulated luminescence methods. The study will lead to improved subsurface salinity detection methods and a better understanding of the consequences of deposition of large volumes of dense saline fluids over shallow freshwater aquifers that result from large-scale environmental disasters, such as tsunamis (e.g., Indonesia, Bangladesh in 2005) and hurricanes (e.g., Mississippi and Louisiana, U.S., 2005). These physically based models may also be applicable to dune-lake systems in other regions, where dune lake systems play an important role in local hydrology and water resources (e.g., China, Niger, Australia). The project will support a number of undergraduate and graduate students from the University of Nebraska, Indiana University, and Oklahoma State University. In addition, we will directly involve K-12 students and teachers in Western Nebraska where the density of population is below 1 person per square km. The study will bring together hydrologists, geophysicists, and limnologists from Australia and North America.