NORTHPORTALL_RESBELOWSED.SHP: Processed continuous resistivity profile (CRP) data below the sediment water interface from Northport Harbor on Long Island, New York collected from May 12 to May 14, 2008

An investigation of coastal groundwater systems was performed along the north shore of Long Island, New York during May 2008 to constrain nutrient delivery to Northport Harbor and Manhasset Bay by delineating locations of likely groundwater discharge. The embayments are bounded by steep moraines and are underlain by thick fine-grained sediments deposited in proglacial lakes during the last ice age. Beach sand and gravel overlie the glacial deposits along the coast. The continuous resistivity profiling (CRP) surveys that were conducted indicate the existence of low-salinity groundwater in shore-parallel bands, typically 25 to 50 meters wide, along the shorelines of both bays. Piezometer sampling and seepage meter deployments in intertidal and subtidal areas of the two bays confirmed the presence and discharge of brackish and low-salinity groundwater. The large tidal ranges (up to 3 meters), and the steep onshore topography and hydraulic gradients are important variables controlling coastal groundwater discharge in these areas. For more information on the survey involved in this project, see http://quashnet.er.usgs.gov/data/2008/08007/.

2008年5月，研究团队于美国纽约州长岛北岸开展沿海地下水系统调查，旨在通过划定潜在地下水排泄点位，明确向北港港（Northport Harbor）与曼赫塞特湾（Manhasset Bay）的营养盐输送情况。该两处海湾被陡峭冰碛物（moraines）环绕，下伏有末次冰期冰前湖（proglacial lakes）沉积的厚层细粒沉积物；沿岸的冰川沉积物之上覆盖有海滩砂与砾石。本次开展的连续电阻率剖面（Continuous Resistivity Profiling, CRP）测量结果显示，两处海湾沿岸均存在与岸线平行的低盐度地下水带，带宽通常为25至50米。研究团队在两处海湾的潮间带（intertidal areas）与潮下带（subtidal areas）布设孔隙水压力计（piezometer）采样装置与渗流计（seepage meter），验证了微咸水与低盐度地下水的存在及其排泄过程。该区域的大型潮差（最大可达3米）、陡峭的陆上地形与水力梯度，是控制该区域沿海地下水排泄的关键影响因子。如需了解本项目相关调查的更多细节，请访问：http://quashnet.er.usgs.gov/data/2008/08007/