scholarly journals Groundwater Flow Modeling in Coastal Aquifers: The Influence of Submarine Groundwater Discharge on the Position of the Saltwater-Freshwater Interface

2016 ◽  
Vol 19 (01) ◽  
Author(s):  
Haile Arefayne Shishaye
Keyword(s):  
Groundwater Flow ◽  
Coastal Aquifers ◽  
Submarine Groundwater Discharge ◽  
Groundwater Discharge ◽  
Flow Modeling ◽  
Groundwater Flow Modeling ◽  
Submarine Groundwater

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

2021 ◽  
Author(s):  
Samrit Luoma ◽  
Juha Majaniemi ◽  
Arto Pullinen ◽  
Juha Mursu ◽  
Joonas J. Virtasalo
Keyword(s):  
Hydraulic Conductivity ◽  
Groundwater Flow ◽  
Baltic Sea ◽  
Submarine Groundwater Discharge ◽  
Flow Model ◽  
Groundwater Discharge ◽  
Coarse Grained ◽  
Local Geometry ◽  
Groundwater Flow Model ◽  
Submarine Groundwater

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

scholarly journals Seawater Intrusion into Coastal Aquifers

Water ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 2719
Author(s):  
Eyal Shalev
Keyword(s):  
Seawater Intrusion ◽  
Coastal Aquifers ◽  
Submarine Groundwater Discharge ◽  
Groundwater Discharge ◽  
Climate Variations ◽  
Special Issue ◽  
Groundwater Exploitation ◽  
Major Constraint ◽  
Highly Sensitive ◽  
Submarine Groundwater

This editorial presents a representative collection of 11 papers presented in the Special Issue on Seawater Intrusion into coastal aquifers. Coastal aquifers are one of the most important water resources in the world. In addition, the natural discharge of freshwater to the sea as submarine groundwater discharge (SGD) has an important role in the ecology of marine environments. The dynamics of seawater and freshwater within coastal aquifers are highly sensitive to disturbances, and their inappropriate management may lead to the deterioration of water quality. In many coastal aquifers, seawater intrusion has become the major constraint imposed on groundwater utilization. Groundwater exploitation and climate variations create dynamic conditions, which can significantly increase seawater intrusion into aquifers and may result in the salinization of wells.

scholarly journals Technical Note: Groundwater flow modeling in coastal aquifers – the influence of submarine groundwater discharge on the position of the saltwater–freshwater interface

2015 ◽  
Vol 12 (4) ◽  
pp. 3753-3785 ◽  
Author(s):  
H. A. Shishaye
Keyword(s):  
Submarine Groundwater Discharge ◽  
Groundwater Discharge ◽  
Analytic Solutions ◽  
Technical Note ◽  
Flow Modeling ◽  
Interface Position ◽  
Aquifer Systems ◽  
Submarine Groundwater ◽  
Interface Location ◽  
The Impact

Abstract. An investigation of the impact of submarine groundwater discharge on the position of saltwater–freshwater interface is presented in this manuscript. Two conceptualizations were considered and analyzed using both analytic and numerical techniques, for comparison purposes. The first conceptualization assumes that the tip of the saltwater–freshwater interface occurs at the shoreline, and the second conceptualization allows for the tip to extend off-shore. Analytic solutions exist for both conceptualizations, i.e., Strack (1976) for conceptualization 1 and Bakker (2006) for conceptualization 2. Results from both analytic and numeric analysis for the two conceptualizations are presented. Results from the first conceptualization were found to overestimate the inland distance to the interface toe, compared to the second conceptualization, for it ignores the influence of submarine groundwater discharge on the interface location. Moreover, results from the analytic solutions as a whole were found to overestimate the interface location compared to the numerical modeling results, for analytic solutions are based on the sharp interface approximations. Therefore, an empirically derived dispersion factor should be used to correct the analytic solution results so as to compare them with the numerically simulated values. Furthermore, offshore model extents should be incorporated when modeling coastal aquifer systems to include the influence of submarine groundwater discharge on the saltwater–freshwater interface position.

scholarly journals Saltwater Intrusion and Submarine Groundwater Discharge: Acceleration of Biogeochemical Reactions in Changing Coastal Aquifers

2021 ◽  
Vol 9 ◽  
Author(s):  
Willard S. Moore ◽  
Samantha B. Joye
Keyword(s):  
Sea Level ◽  
Coastal Aquifers ◽  
Submarine Groundwater Discharge ◽  
Saltwater Intrusion ◽  
Groundwater Discharge ◽  
Chemical Species ◽  
Oxidative Capacity ◽  
Fluid Mixture ◽  
Submarine Groundwater ◽  
Subterranean Estuaries

Intrusion of saltwater into freshwater coastal aquifers poisons an essential resource. Such intrusions are occurring along coastlines worldwide due largely to the over-pumping of freshwater and sea level rise. Saltwater intrusion impacts drinking water, agriculture and industry, and causes profound changes in the biogeochemistry of the affected aquifers, the dynamic systems called subterranean estuaries. Subterranean estuaries receive freshwater from land and saltwater from the ocean and expose this fluid mixture to intense biogeochemical dynamics as it interacts with the aquifer and aquiclude solids. Increased saltwater intrusion alters the ionic strength and oxidative capacity of these systems, resulting in elevated concentrations of certain chemical species in the groundwater, which flows from subterranean estuaries into the ocean as submarine groundwater discharge (SGD). These highly altered fluids are enriched in nutrients, carbon, trace gases, sulfide, metals, and radionuclides. Seawater intrusion expands the subterranean estuary. Climate change amplifies sea level variations on short and seasonal time scales. These changes may result in higher SGD fluxes, further accelerating release of nutrients and thus promoting biological productivity in nutrient-depleted waters. But this process may also adversely affect the environment and alter the local ecology. Research on saltwater intrusion and SGD has largely been undertaken by different groups. We demonstrate that these two processes are linked in ways that neither group has articulated effectively to date.

scholarly journals Storm-Driven Fresh Submarine Groundwater Discharge and Nutrient Fluxes From a Barrier Island

2021 ◽  
Vol 8 ◽  
Author(s):  
Dini Adyasari ◽  
Daniel Montiel ◽  
Behzad Mortazavi ◽  
Natasha Dimova
Keyword(s):  
Spatial Variability ◽  
Groundwater Flow ◽  
Coastal Area ◽  
Submarine Groundwater Discharge ◽  
Groundwater Discharge ◽  
Barrier Island ◽  
Barrier Islands ◽  
Nutrient Fluxes ◽  
Storm Events ◽  
Submarine Groundwater

Quantifying and characterizing groundwater flow and discharge from barrier islands to coastal waters is crucial for assessing freshwater resources and contaminant transport to the ocean. In this study, we examined the groundwater hydrological response, discharge, and associated nutrient fluxes in Dauphin Island, a barrier island located in the northeastern Gulf of Mexico. We employed radon (222Rn) and radium (Ra) isotopes as tracers to evaluate the temporal and spatial variability of fresh and recirculated submarine groundwater discharge (SGD) in the nearshore waters. The results from a 40-day continuous 222Rn time series conducted during a rainy season suggest that the coastal area surrounding Dauphin Island was river-dominated in the days after storm events. Groundwater response was detected about 1 week after the precipitation and peak river discharge. During the period when SGD was a factor in the nutrient budget of the coastal area, the total SGD rates were as high as 1.36 m day–1, or almost three times higher than detected fluxes during the river-dominated period. We found from a three-endmember Ra mixing model that most of the SGD from the barrier island was composed of fresh groundwater. SGD was driven by marine and terrestrial forces, and focused on the southeastern part of the island. We observed spatial variability of nutrients in the subterranean estuary across this part of the island. Reduced nitrogen (i.e., NH4+ and dissolved organic nitrogen) fluxes dominated the eastern shore with average rates of 4.88 and 5.20 mmol m–2 day–1, respectively. In contrast, NO3– was prevalent along the south-central shore, which has significant tourism developments. The contrasting nutrient dynamics resulted in N- and P-limited coastal water in the different parts of the island. This study emphasizes the importance of understanding groundwater flow and dynamics in barrier islands, particularly those urbanized, prone to storm events, or located near large estuaries.

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