Geophysical Monitoring of Groundwater-Lake Interactions

地下水-地表水相互作用是一个新兴的研究领域。迫切需要确定水量平衡，跟踪污染物在界面上的移动(向两个方向)，并了解地下水排放对地表水生境的影响。但是，进行必要的测量仍然存在障碍。使用质量平衡计算和模型进行的流量估算不能提供地下水排放和补给的位置。使用渗流计、压力计和沉淀物K进行的点测量一直受到空间覆盖不足和重复性问题的困扰。这项研究将使用新开发的海洋电阻率系统绘制两个有良好记录的地点-宾夕法尼亚州的拉卡瓦湖和新罕布夏州的镜湖-地下水补给区和排泄区的范围和连续性。通过在浮线上拖曳电极收集的测量结果可以与GPS和水深测量数据结合起来，在数据反演过程中产生几乎连续的二维电阻率剖面。电阻率随孔隙度、孔隙流体离子强度和粘土含量的变化而变化。在某些情况下，孔隙流体的变化指示地下水从湖泊补给(渗漏)或排入湖泊(渗漏)。孔隙度的增加可能指示可能的泄漏区，粘土含量的增加可能指示地下水-地表水相互作用受限的区域。利用电阻率系统，可以在更大的区域内进行测量，并与湖底的地质情况进行比较。对地下水渗漏或渗漏潜在区域的地球物理解释将进行测试，方法是部署一系列低成本的人工渗漏仪，以及利用电磁流量计检测流量随时间变化的新型测井渗漏仪。地球物理调查将通过提供更好的空间覆盖范围、地质特征和渗流之间的联系以及更多的时间数据来促进对地下水-湖泊相互作用的了解，以检查系统对压力(包括风暴和气候变化)的响应。由于淡水资源面临的压力越来越大，这项研究对社会具有重要意义。更好地了解地下水与地表水的相互作用将提高对水量平衡和化学迁移(即污染物)的预测。此外，渗流界面往往是生物活动的热点，在营养和碳循环中发挥着重要作用。这项研究旨在转移到其他地点，因为它着眼于地球物理信号(S)和观测水文之间的基本关系。这项研究的教育影响发生在多个层面。将为三名硕士研究生在第二年的学习提供资金。此外，本科生将担任现场助理，并承担研究子项目的所有权。为了进一步加强他们的研究经验，包括允许本科生参加科学会议并展示他们的研究成果的资金。寺庙经常吸引第一代大学生，少数民族人口占30%；在地质系，学生中有很好的性别平衡。因此，坦普尔能够接触到科学界代表性不足的群体。除了大学教育，该项目还将提供有关地下水与湖泊相互作用的重要性的教育材料，供在所研究的湖泊旅游时使用。

0509853ToranGroundwater-surface water interactions are an emerging area of research. Thereis a critical need to determine water budgets, to track contaminants moving across theinterface (in either direction), and to understand the influence of groundwater dischargeon surface water habitats. But obstacles remain to making the necessary measurements.Flux estimates made using mass balance calculations and models do not provide locationsof groundwater discharge and recharge. Point measurements made using seepage metersor piezometers and sediment K have been plagued by lack of spatial coverage andreproducibility problems.This research will map the extent and continuity of groundwater recharge anddischarge zones at two well-documented sites, Lake Lacawac in Pennsylvania and MirrorLake in New Hampshire, using a newly-developed marine resistivity system.Measurements collected by towing the electrodes behind the boat on a floating line canbe combined with GPS and bathymetry data during data inversion to produce nearlycontinuous 2-D resistivity profiles. Resistivity responds to variation in porosity, ionicstrength of pore fluids, and clay content. In some cases, changes in pore fluid indicategroundwater recharge from the lake (outseepage) or discharge to the lake (seepage).Increase in porosity may indicate likely areas of discharge and increased clay contentmay indicate areas of restricted groundwater-surface water interaction. Using theresistivity system, measurements can be made over larger areas, and compared with thegeology beneath the lake. The geophysical interpretation of potential areas ofgroundwater seepage or outseepage will tested by deploying an array of low cost manualseepage meters, as well as new logging seepage meters that make use of anelectromagnetic flowmeter to detect changes in flow over time. The geophysical surveyswill advance knowledge of groundwater-lake interactions by providing better spatialcoverage, linkages between geologic features and seepage, and more temporal data inorder to examine system response to stresses (both storms and climate change).This research is important to society because of the increasing pressures onfreshwater resources. Better understanding groundwater-surface water interactions willimprove prediction of water budgets and chemical transfer (i.e., contaminants).Furthermore, seepage interfaces are often hot spots of biological activity and play animportant role in nutrient and carbon cycling. This study is designed for transfer to othersites because it looks at the fundamental relationships between the geophysical signal(s)and the observed hydrology.The educational impact of this research occurs at multiple levels. Funds will beprovided for three masters students during their second year of study. In addition,undergraduates will act as field assistants and take ownership of research sub-projects. Tofurther enhance their research experience, funding is included to permit undergraduatestudents to attend a scientific conference and present their research. Temple often attractsfirst-generation college students and has a 30% minority population; in the geologydepartment, there is a good gender balance among students. Thus, Temple is able toreach under-represented groups in the sciences. In addition to university education, theproject will contribute educational materials on the importance of groundwater-lakeinteraction for tours at the lakes studied.