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

沙丘含水层系统有数百个浅湖，盐度从淡水到超过100 g/L不等，到目前为止，人们对产生和维持这些巨大盐度梯度的机制知之甚少。在这项研究中，我们计划确定沙丘含水层系统中观察到的湖泊盐度的时空变化是否源于：1)地下水流入/流出与湖泊蒸发比率的差异，或2)当地和区域尺度地下水流动系统向湖泊输送溶质的空间差异。为了检验这些不同的湖泊盐碱化端元假说，我们将为我们的研究区开发详细的三维变密度地下水流动、溶质运移和地表水-地下水相互作用模型。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，以表征近湖含水层带的地表/地下溶质分布。我们将使用硅藻和光激发发光方法来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难造成的浅层淡水含水层上大量高密度咸水流体沉积的后果，如海啸(如印度尼西亚、孟加拉国，2005年)和飓风(如密西西比州和路易斯安那州，美国，2005年)。这些基于物理的模型也可能适用于其他地区的沙丘-湖泊系统，那里的沙丘-湖泊系统在当地的水文和水资源中发挥着重要作用(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。这项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。

0609982ZlotnikThe 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.