Geological and groundwater flow model of a submarine groundwater discharge site at Hanko (Finland), northern Baltic Sea

Abstract Three-dimensional geological and groundwater flow models of a submarine discharge (SGD) site at Hanko (Finland), in the northern Baltic Sea, have been developed to provide framework tool for estimation SGD rates into coastal sea. The dataset used consists gravimetric, ground-penetrating radar shallow seismic surveys, drill logs, level monitoring data, field observations, LiDAR digital elevation model. model is constrained by local geometry late Pleistocene Holocene deposits, including till, glacial coarse-grained fine-grained sediments, post-glacial mud, littoral aeolian deposits. aquifer sediments form shore platform that extends approximately 100–250 m offshore, where unit slopes steeply seawards becomes covered muds. Groundwater preferentially takes place channel-fill outwash sand gravel interbeds conduits higher hydraulic conductivity, led formation pockmarks on seafloor areas thin or absent mud cover. estimated average rate per square meter 0.22 cm day −1 autumn 2017. increased 0.28 as response an 30% increase recharge spring 2020. Sensitivity analysis shows has larger influence compared with conductivity conductance. An this region will cause more Sea.