scholarly journals Evaluation of Temperature Profiling and Seepage Meter Methods for Quantifying Submarine Groundwater Discharge to Coastal Lagoons: Impacts of Saltwater Intrusion and the Associated Thermal Regime

Water ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1648 ◽  
Author(s):  
Joel Tirado-Conde ◽  
Peter Engesgaard ◽  
Sachin Karan ◽  
Sascha Müller ◽  
Carlos Duque
Keyword(s):  
Thermal Regime ◽  
Coastal Lagoons ◽  
Groundwater Discharge ◽  
Thermal Methods ◽  
Fresh Groundwater ◽  
Lagoon Water ◽  
Seepage Meter ◽  
Vertical Heterogeneity ◽  
Key Factor ◽  
Heat Transport Equation

Surface water-groundwater interactions were studied in a coastal lagoon performing 180 seepage meter measurements and using heat as a tracer in 30 locations along a lagoon inlet. The direct seepage meter measurements were compared with the results from analytical solutions for the 1D heat transport equation in three different scenarios: (1) Homogeneous bulk thermal conductivity (Ke); (2) horizontal heterogeneity in Ke; and (3) horizontal and vertical heterogeneity in Ke. The proportion of fresh groundwater and saline recirculated lagoon water collected from the seepage experiment was used to infer the location of the saline wedge and its effect on both the seepage meter results and the thermal regime in the lagoon bed, conditioning the use of the thermal methods. The different scenarios provided the basis for a better understanding of the underlying processes in a coastal groundwater-discharging area, a key factor to apply the best-suited method to characterize such processes. The thermal methods were more reliable in areas with high fresh groundwater discharge than in areas with high recirculation of saline lagoon water. The seepage meter experiments highlighted the importance of geochemical water sampling to estimate the origin of the exchanged water through the lagoon bed.

scholarly journals Submarine Groundwater Discharge From Sediments and Sand Boils Quantified by the Mean Residence Time of a Tracer Injection

2021 ◽  
Vol 9 ◽  
Author(s):  
Michael Schlüter ◽  
Philipp Maier
Keyword(s):  
Residence Time ◽  
Mean Residence Time ◽  
Submarine Groundwater Discharge ◽  
Groundwater Discharge ◽  
Tracer Injection ◽  
Discharge Rates ◽  
Seepage Meter ◽  
Submarine Groundwater ◽  
Sand Boils ◽  
The Mean

To quantify submarine groundwater discharge, we developed an inexpensive automated seepage meter that applies a tracer injection and the computation of the mean residence time. The SGD-MRT is designed to measure a wide range of discharge rates from about 30 to 800 cm³/min and allows minimizing backpressures caused by pipe friction or flow sensors. By modifying the inner volume of the flow-through unit, the range of measurement is adjustable to lower or higher discharge rates. For process control and data acquisition, an Arduino controller board is used. In addition, components like temperature, conductivity, and pressure sensors or pumps extend the scope of the seepage meter. During field tests in the Wadden Sea, covering tidal cycles, discharge rates of more than 700 cm³/min were released from sand boils. Based on the measured discharge rates and numerical integration of the time series data, a water volume of about 400 dm3 with a seawater content of less than 12% was released from the sand boil within 7 h.

Submarine groundwater discharge (SGD) in the springs of Sahlenburg tidal flat, Germany: a geochemical approach. 

2021 ◽  
Author(s):  
Roger Carvalho da Silva ◽  
Hannelore Waska ◽  
Kai Schwalfenberg ◽  
Thorsten Dittmar
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Tidal Flat ◽  
Submarine Groundwater Discharge ◽  
Groundwater Discharge ◽  
Fresh Groundwater ◽  
Large Reservoir ◽  
Flat Area ◽  
Submarine Groundwater ◽  
Groundwater Springs

<p>Submarine groundwater discharge (SGD) is an important connection between fresh groundwater and the marine ecosystem. The scientific interest in SGD has grown considerably during the last decades due to the recognition of SGD in coastal environments as a significant source of nutrients and pollutants.  The Sahlenburg area (Northern Germany) is known by its highly permeable sediments and high rainfall precipitation that produces a large reservoir of groundwater.  Such characteristics are essential for industry, agriculture and drinking water supply with a large regional importance. In addition, this groundwater discharges in the form of highly productive springs directly into the adjacent tidal flats, with so far unknown effects on the local biogeochemistry.  The aim of this study was to characterize the spatial distribution of salinity, fluorescence dissolved organic matter (FDOM), dissolved organic matter (DOC) and total dissolved nitrogen (TDN) of the springs of Sahlenburg tidal flat area in Cuxhaven, Germany. We hypothesize that the SGD composition is changing on its way through the tidal flat due to biogeochemical factors. This may affect the composition of the water in the final part of the pathway with more influence of seawater. Porewater springs were sampled in February 2019 during low tide in three different types of locations in the tidal flat area: nearshore where the springs are located close to the vegetated shoreline (salt marsh), offshore approximately 70 meters from the vegetation and in the middle from both locations. In addition, porewater from a nearby sandy beach (around 500 meters away from the area of spring sampling), and surface samples from a nearby lake and seawater, were obtained. Salinity and FDOM were measured in situ, and DOC and TDN in the laboratory.  The preliminary data showed low average values for salinity in all springs (0.2-1.4), as well as in beach porewater, indicating strong influence of fresh groundwater in the whole area. When comparing the three spring location types, the lowest salinities were found offshore, and the highest nearshore. This difference could be due to the size of the springs, since nearshore springs usually were smaller when compared to offshore springs. Furthermore, depressions in the tidal flat relief close to nearshore springs favored seawater retention in pools during low tide. Additionally, we found higher average values for DOC and FDOM in the nearshore when compared with the other spring areas, but lower compared to the lake, beach porewater and seawater. The average values for TDN (272-452 µmol L<sup>-1</sup>) in the groundwater springs were higher when compared to all other sample types (beach porewater, seawater, and lake water) in this study. These values suggest an anthropogenic input (e.g., agriculture influence) in the surrounding watershed and might stimulate primary productivity in the tidal flat. We conclude that groundwater springs in Sahlenburg tidal flat differ locally in their biogeochemistry due to different residence times, heterogeneity of sediment layers, and size of the springs.</p><p> </p>

Effect of subsurface dams on saltwater intrusion and fresh groundwater discharge

2019 ◽  
Vol 576 ◽  
pp. 508-519 ◽  
Author(s):  
Qinpeng Chang ◽  
Tianyuan Zheng ◽  
Xilai Zheng ◽  
Bo Zhang ◽  
Qiguo Sun ◽  
...  
Keyword(s):  
Saltwater Intrusion ◽  
Groundwater Discharge ◽  
Fresh Groundwater

scholarly journals Studies on Groundwater Problems in an Area Subjected to Sea Water Ingression and Seepage Into Groundwater in Karaikal District Using GIS

2018 ◽  
Vol 7 (3.10) ◽  
pp. 150
Author(s):  
T Subramani ◽  
P Krishnan
Keyword(s):  
Water Quality ◽  
Coastal Waters ◽  
Submarine Groundwater Discharge ◽  
Sea Water ◽  
Groundwater Discharge ◽  
Treated Wastewater ◽  
Coastal Zones ◽  
Fresh Groundwater ◽  
Submarine Groundwater ◽  
Pumping Rates

Fresh groundwater quality and accessibility in coastal zones is influenced via seawater interruption into coastal aquifers, and coastal water quality and biological community status might be altogether influenced by groundwater pollutants that are transported into coastal waters by submarine groundwater discharge (SGD). SGD and its pertinent evaluation as one associating part  among the different principle local pathways of freshwater and tracer/poison contributions from land to sea and the coordinated framework working of both and as primary segments of the same coastal groundwater framework. An elective technique might be to control seawater interruption through fake groundwater revive, for example by adequately treated wastewater, which may impressively decrease long haul patterns of saltiness increment in pumped groundwater, notwithstanding for little simulated energize rates contrasted with pumping rates. Both the outside sources and the interior wellsprings of water seepage might be distinguished via doing infrared thermo-realistic assessments subsequent to directing water snugness tests, flooding tests or pressure driven tests as suitable. A contextual investigation was led to discover the examinations on groundwater issues in a region subjected to sea water ingression and seepage into groundwater in Karaikal   

Multi-method approach combining isotopic tracers, anthropogenic contaminants and mapping to retrace socio-environmental trajectories of groundwater-dependent coastal hydrosystems

2020 ◽  
Author(s):  
Melanie Erostate ◽  
Frederic Huneau ◽  
Emilie Garel ◽  
Vanina Pasqualini
Keyword(s):  
Water Resources ◽  
Temporal Dynamics ◽  
Coastal Lagoons ◽  
Management Strategies ◽  
Current Status ◽  
Fresh Groundwater ◽  
Isotopic Tracers ◽  
Goods And Services ◽  
Wide Range ◽  
Multi Method Approach

<p>Coastal lagoons are unique and complex ecosystems. Resulting from both terrestrial (fresh groundwater and surface water) and marine water influences, these ecosystems are often maintained by direct or indirect groundwater supplies and collectively known as groundwater dependent ecosystems (GDEs). Because they provide a wide range of ecosystem goods and services on which a large part of the human population depends, coastal GDEs are considered as complex socio-economic and ecological component worldwide. The increasing human development in coastal areas induces yet a strong pressure on water resources and the expected effects of climate change could exacerbate the pressures on these environments. To limit the risks of degradation and to ensure the sustainability of ecosystem services, the implementation of proper water resources management strategies is essential. This requires a strong knowledge of the environmental and socio-economic trajectories of hydrosystems, and particularly of the behavior and role of groundwater.</p><p>To this end, only the combined use of several tools allows a global understanding of the spatial and temporal dynamics of the system. The correlation between isotopic tracers (<sup>18</sup>O, <sup>2</sup>H, <sup>3</sup>H, <sup>15</sup>N, <sup>11</sup>B), anthropogenic contaminants (organic micro pollutants) and mapping approaches (land-use and vulnerability) allows a historical analyze of the hydrosystem. In addition, to better constraint the hydrosystem hydrological behavior, it is also possible to highlight the current status of water resources, the historical legacy of pollutants and the consequences of past developments and practices, which continue to jeopardize the current quality of the water resource. This methodology was applied to a Mediterranean hydrosystem, in connection with a coastal lagoon (Corsica Island, France). The identification of degradation processes and their chronology could then be traced back in time.</p><p>It appears that the current deterioration is mainly due to a legacy pollution resulting from the development of policies implemented 60 years earlier. In the case of coastal GDEs that are highly anthropized and subject to ever-increasing development, this methodology proposes new key elements for the establishment of relevant management strategies to ensure the future sustainability of water resources.</p>

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