RES2DINV format continuous resistivity profile data collected in Northport Harbor on Long Island, New York on May 12, 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海岸地下水系统调查，旨在通过圈定潜在地下水排泄点位置，明确输入至诺斯波特港（Northport Harbor）与曼赫塞特湾（Manhasset Bay）的营养盐输送量。两处海湾均以陡峭的冰碛丘陵为界，末次冰期冰前湖沉积的厚层细粒沉积物构成其基底。沿岸区域的海滩砂与砾石覆盖于冰川沉积层之上。本次开展的连续电阻率剖面法（Continuous Resistivity Profiling, CRP）调查结果显示，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与潮下带区域开展测压管采样与渗流计布设工作，证实了微咸水与低盐度地下水的存在及其排泄过程。较大的潮差（最大可达3米）、陡峭的陆上地形与水力梯度，是控制该区域海岸地下水排泄的关键调控变量。如需了解本项目相关调查的更多细节，可访问：http://quashnet.er.usgs.gov/data/2008/08007/。