RES2DINV format continuous resistivity profile data collected in Manhasset Bay on Long Island, New York on May 15, 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 https://cmgds.marine.usgs.gov/fan_info.php?fan=2008-007-FA.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，旨在通过圈定潜在地下水排泄点位，限定输入至诺斯波特港（Northport Harbor）与曼哈塞特湾（Manhasset Bay）的营养盐通量。上述海湾以陡峭冰碛垄为界，其下伏有末次冰期冰前湖沉积的厚层细粒沉积物；沿岸区域的海滩砂与砾石覆盖于冰碛沉积物之上。本次调查开展的连续电阻率剖面法（continuous resistivity profiling, CRP）结果显示，两处海湾的岸线均存在平行岸线分布的低盐地下水条带，条带宽度通常为25至50米。针对两处海湾潮间带与潮下带区域开展的测压管采样及渗流仪布设工作，证实了半咸水与低盐地下水的存在及其排泄过程。该区域最大潮差可达3米，加之陡峭的陆上地形与水力梯度，是控制沿海地下水排泄的关键影响因素。如需了解本项目调查的更多细节，可访问https://cmgds.marine.usgs.gov/fan_info.php?fan=2008-007-FA。