Simulated Saltwater Intrusion in the Bedrock with No Sea Level Rise

Groundwater modeling was used to simulate the effects of sea-level rise on groundwater levels in the New Hampshire Seacoast. The MODFLOW-USG Transport model (Panday, 2022) was used to simulate groundwater flow and saltwater intrusion in these communities. This map shows relative salinity (0=freshwater-blue,1=saltwater-red). SWI was simulated for Rollinsford, Dover, Madbury, Durham, Newmarket, Newfields, Exeter, Newington, Portsmouth, New Castle, and parts of Rye and Stratham. SWI was not simulated in the southern portion of the NH Seacoast, including parts of Rye and Stratham, Greenland, North Hampton, Hampton, Hampton Falls, and Seabrook. The SWI modeling produced estimates of relative salinity in groundwater at various depths ranging from approximately 10 feet to more than 800 feet. This map shows SWI in bedrock approximately 800 feet below MSL. There is substantial uncertainty in these estimates due to limited knowledge of bedrock fracturing and other subsurface parameters. These model results and maps provide a first-cut estimate of saltwater intrusion and should be enhanced and/or verified by field measurements.本研究借助地下水建模手段，模拟海平面上升对新罕布什尔州海岸带（New Hampshire Seacoast）地下水位的影响。本次模拟采用MODFLOW-USG 溶质运移模型（MODFLOW-USG Transport model，Panday, 2022），以刻画该区域的地下水流动与盐水入侵过程。本图展示了相对盐度分布规则：0代表淡水，对应蓝色；1代表盐水，对应红色。本次盐水入侵（Saltwater Intrusion，下文简称SWI）模拟覆盖罗林斯福德（Rollinsford）、多佛（Dover）、马德伯里（Madbury）、达勒姆（Durham）、纽马克特（Newmarket）、纽菲尔德（Newfields）、埃克塞特（Exeter）、纽因顿（Newington）、朴次茅斯（Portsmouth）、纽卡斯尔（New Castle），以及赖伊（Rye）和斯特拉瑟姆（Stratham）的部分区域。新罕布什尔州海岸带南部区域未开展SWI模拟，涉及区域包括格陵兰（Greenland）、北汉普顿（North Hampton）、汉普顿（Hampton）、汉普顿福尔斯（Hampton Falls）、西布鲁克（Seabrook），以及赖伊和斯特拉瑟姆的部分区域。本次SWI模拟得到了不同深度地下水中的相对盐度估算值，深度区间约为10英尺至800英尺以上。本图展示了距平均海平面（Mean Sea Level，MSL）约800英尺的基岩中的SWI分布情况。由于对基岩裂隙及其他地下参数的认知不足，上述估算结果存在较大不确定性。上述模型结果与图集仅为盐水入侵的初步估算成果，需通过野外实测数据进行完善与验证。