Navigation, bathymetry, and water temperature points of ship position during continuous resistivity profile data collection in Northport Harbor on Long Island, New York in May, 2008 (RESGPSPNTS_NORTHPORT.SHP)

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，明确向北港港（Northport Harbor）与曼哈塞特湾（Manhasset Bay）的营养盐输送通量。该两处海湾被陡峭冰碛物环绕，其下伏有末次冰期冰前湖沉积的厚层细粒沉积物；沿海岸线的冰碛物之上覆有海滩砂与砾石。本次实施的连续电阻率剖面法（continuous resistivity profiling, CRP）调查显示，两处海湾岸线沿线存在宽度通常为25至50米的平行岸线低盐地下水条带。通过在两处海湾的潮间带与潮下带开展测压管取样与渗流仪布设工作，证实了半咸水与低盐地下水的存在及其排泄过程。较大的潮差（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变量。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.