RES2DINV format continuous resistivity profile data collected in Northport Harbor on Long Island, New York on May 13, 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（Long Island）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，明确向北港港（Northport Harbor）与曼哈塞特湾（Manhasset Bay）输送的营养盐通量。该两处海湾被陡峭的冰碛丘陵围限，其基底为末次冰期冰前湖沉积的厚层细粒沉积物；沿岸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）测量结果显示，两处海湾的岸线沿线存在与岸线平行的低盐度地下水带，带宽通常为25至50米。研究人员在两处海湾的潮间带与潮下带区域开展渗压计采样与渗流计布设工作，监测结果证实了微咸水与低盐度地下水的存在及其排泄过程。该区域的大潮差（最大可达3米）、陡峭的陆上地形以及水力梯度，是控制海岸地下水排泄的关键影响因素。如需了解本项目相关调查的更多信息，请访问：https://cmgds.marine.usgs.gov/fan_info.php?fan=2008-007-FA。