Groundwater and Salinity Responses to Land Reclamation in Jiaozhou Bay (China): Field Observations and Modeling

Abstract Coastal groundwater dynamics and solute transport are influenced by multiple factors including land reclamation, evaporation, and tidal fluctuations. However, their quantitative impacts on groundwater flow and salinity distribution in large‐scale muddy tidal flats remain insufficiently understood. This study combines field measurements and numerical simulations to investigate hydraulic heads and groundwater salinity over a spring‐neap tidal cycle in a muddy intertidal transect at Jiaozhou Bay, China. Results show that seepage‐face evaporation significantly increases groundwater salinity toward land, with its intensity modulated by seasonal variability. Based on field observations, we propose a new concept of tidal run‐up, which highlights its role in elevating landward hydraulic heads during rising and high tides. Land reclamation significantly alters groundwater flow patterns, transforming the original multiple circulation cells into a single, large cell in which inland groundwater discharges across the entire intertidal zone. Salinity distribution is jointly controlled by inland freshwater input, evaporation, and tidal forcing. Numerical simulations reveal that land reclamation reduces both outflow and inflow fluxes, and the outflow fluxes along the aquifer‐ocean interface decrease from 12.1 m 2 /d before reclamation to 7.7 m 2 /d after reclamation during the observation period, with evaporation contributing 56% and 31% of the total outflow flux, respectively. These findings enhance the understanding of groundwater flow and solute transport in large‐scale muddy tidal flats, and offer important implications for biogeochemical processes in intertidal zones.