Quantifying tidal contribution to submarine groundwater discharges: A review

Abstract

Submarine groundwater discharges (SGD), consisting of groundwater flow from both terrestrial and marine origins, is an important source of nutrients, contaminants, and other chemicals to the coastal waters, and has significant impacts and implications on coastal environment and ecology. This paper reviews the recent advances in quantifying the tide-induced SGD in various beach aquifers around the world by means of mathematical modeling, laboratory experiments, and field observations or their combinations. Numerous studies have shown that (1) the order of magnitude of SGD around the world estimated by radium isotope tracers typically ranges from 10 2 to 10 3 m 3 d 1 m 1 of the shoreline, (2) SGD is mainly of marine origin, i.e. the re-circulated seawater across the aquifer-sea interface, and (3) tide is one of the major forces driving seawater-groundwater circulation. The order of magnitude of the tidal contributions to SGD from beach aquifers reported in the literature is only 10 m 3 d 1 m 1 length of shoreline, at least one order of magnitude smaller than the total SGD estimated by radium isotope tracers. This is obviously in contradiction with (3). The possible reasons for this contradiction may include (1) underestimation of the shoreline length due to neglecting many headlands, bays and banks of tidal rivers, and (2) negligence of the seawater-groundwater exchange from the seabed ranging from the nearshore areas to the continental shelf. Further research is needed to understand more about the contradiction.submarine groundwater discharges (SGD), radium isotope tracer method, numerical model of beach aquifer, densitydependent flow, tide-induced SGD Citation: Li H L, Jiao J J. Quantifying tidal contribution to submarine groundwater discharges: A review.

Estimation of seawater–groundwater exchange rate: case study in a tidal flat with a large-scale seepage face (Laizhou Bay, China)

“…Since the sediment samples were subjected to compaction and perturbation during each of the Darcy column tests, K F obtained by the in-situ method was used in the calculation of the water exchange rate. As the values of K V and K F are very close to each other and the estimated SGD is 8.8 m 3 d −1 m −1 , it is reasonable to consider that the order of magnitude of SGD is ∼10 m 3 d −1 m −1 , which is in line with previous studies reviewed by Li and Jiao (2013).…”

“…Since the 1990s, there has been growing interest in quantifying SGD to ecologists, geochemists and biologists for its important role as a channel for transporting nutrients, contaminants and other chemicals from land to sea (Li et al 1999;Slomp and Cappellen 2004). Li and Jiao (2013) provided a thorough review of previous studies on quantifying tide-induced SGD. The research methods are mainly based on mathematical modeling, field observations, laboratory experiments or their combinations.…”

Terrestrial-originated submarine groundwater discharge through deep multilayered aquifer systems beneath the seafloor

“…The total SGD estimated by the activities of 226 Ra in summer is about 1000 m 3 day −1 m −1 (Moore, ), which includes three parts: (1) SGD within the intertidal zone, (2) SGD from the shallow seafloor near the coastline, and (3) SGD from the deep seafloor. Tide‐induced SGD in the intertidal zone ranges from about 1 to 10 m 3 day −1 m −1 (Li and Jiao, ). Recently, King et al .…”

Seawater-groundwater Exchange in a Silty Tidal Flat in the South Coast of Laizhou Bay, China

“…Submarine groundwater discharge ( SGD) has significant impacts and implications on ecological environment due to its important role in transport of nutrients, contaminations and other chemicals ( Li and Jiao, 2013;Li et al, 1999;Slomp and Cappellen, 2004 ) . An increasing number of scholars have paid attention to SGD estimation.…”