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Wpływ stosowanych praktyk rolniczych na dopływ wód podziemnych oraz azotanów do Zatoki Puckiej

Potrykus Dawid

Przegląd Geologiczny

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2024

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Vol. 72, nr 1

15--25

EN

Eutrophication of marine baśni associated with submarine groundwater discharge is currently one of the most important challenges in modern coastal hydrogeology, and is classified as a serious global environmental problem. Aparticular source of groundwater pollution is agricultural activity, which is commonly carried out in the coastal zone. Research was conducted on arepresentative part of the Bay of Puck watershed, dominated by agriculturall anduse. The geological setting of the study area is heterogeneous, which has a significant influence on groundwater flow and occurrence in the multi-aquifer hydrosystem, draining into Puck Bay. The impact of agricultural practices on groundwater and nitrate discharge to the Puck Bay was determined, byan integrated modeling approach, developed using combination of the SWAT, MODFLOW-NWT and MT3DMS codes. Spatial and seasonal variations of the N-NO3 load leached from the soil profile and the infiltration of precipitation are convergent with observed trends in the discharge of groundwater and N-NO3 loads into Puck Bay. The simulations show that 1,355.13 m3/h of ground- waterand1.87kg/h (16. 4 t/year) of N-NO3 loadare discharged into Puck Bay from the aquifers analyzed, the majority of which comes froman upper aquifer. The distribution of the values as determined was found to be influenced by agricultural practices, resulting from changes in crop structure, fertilizer management, cultivation methods and grazing.

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Groundwater mapping of urban and coastal areas in Brunei

Abidin Hakimmi, Azffri Siti Lieyana, Nirus Emelia, Suhip Asri, Jaya Afiq Aiman, Gödeke Stefan Herwig

Journal of Water and Land Development

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2024

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no. 61

21--29

EN

Groundwater mapping plays an important role in effective water resource management, sustainable development, and environmental protection. In the tropical Brunei Darussalam (north Borneo Island), groundwater mapping is yet to be provided. The aim of the study is to provide groundwater mapping of Brunei, particularly for the urban and coastal areas of the Brunei-Muara capital district. The study uses a GIS interpolation technique to generate a groundwater contour map based on groundwater data from 572 sacrificial boreholes located in the study area. Remote sensing data and published maps from secondary sources were digitised in ArcGIS software to produce thematic layers for further hydrological evaluations. Results showed that groundwater levels in the study area are generally high and shallow, ranging from 0 to 18 m below ground level with a mean value of 2.9 m. According to the evaluation of geo-thematic layers and groundwater contours, groundwater flows towards the South China Sea in the coastal areas and towards the Brunei River further inland. Hydraulic gradients towards the South China Sea also vary between 0.004 and 0.08. Thus, assuming surface aquifer thickness in the weathered zone between 10 to 20 m, hydraulic conductivities ranges from 1∙10-5 to 1∙10-4 m∙s-1, a submarine groundwater discharge (SGD) flux between 4.7∙10-7 to 4.0∙10-4 m3 ∙s-1 per unit width can be estimated for the shallow aquifer. This study provides valuable insights into the groundwater system dynamics so important, which are critical for its future utilisation and protection, aiming to contribute to the national water security in Brunei Darussalam.

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Modeling of Groundwater Pollution by Former Seawater in Submarine Groundwater Discharge Driven by Saltwater Intrusion

Al-Taliby Wissam, Dekhn Hadeel

Journal of Ecological Engineering

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2022

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Vol. 23, nr 2

166--175

EN

Coastal aquifers are usually vulnerable to contamination by saltwater intrusion. The degree of contamination depends on the amount of former seawater intruding the aquifer as submarine groundwater discharge (SGD). A three-dimensional numerical SEAWAT model was developed to provide insights to the responses of saltwater intrusion and amount of seawater portion of SGD, to groundwater withdrawal from four wells at different spatial locations. The results showed that saltwater wedge encroachment varies with a withdrawal rate and well location. Increasing withdrawal rates from 0.165 m3/s to 0.53166 m3/s resulted in a noticeable increase in wedge encroachment into the aquifer from 589 m to 1319 m, respectively, regardless of the distance from the coastline. However, higher withdrawals from the wells closer to the coastline caused the hydraulic head near the seaside to drop below the terrestrial head, causing the saltwater wedge to be pushed back toward the sea. Simulations also showed that a coastal well might act as a hydraulic barrier that prevents the brackish zone from moving further inland, which is critically important in terms of groundwater management. Seawater contributed from 5% to above 33% in SGD. Although the withdrawal rates from Well 3 were 10 to 20 times larger than the Well 2 rates, the seawater contribution associated with Well 3 was about the same. This is attributed to the horizontal vicinity of Well 2 to the seacoast boundary compared to Well 3 even though Well 3 is deeper than Well 2, demonstrating that it is the horizontal location that governs the amount of abstracted former seawater.

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Significance of nutrient fluxes via submarine groundwater discharge in the Bay of Puck, southern Baltic Sea

Szymczycha Beata, Kłostowska Żaneta, Lengier Monika, Dzierzbicka-Głowacka Lidia

Oceanologia

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2020

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No. 62 (2)

117--125

EN

In this study, we collected submarine groundwater discharge (SGD) and seawater samples at six sites in the Bay of Puck, in the southern Baltic Sea, in order to estimate the nutrient distribution in groundwater affected areas. In addition, we estimated nutrient fluxes via SGD, including both fresh SGD (FSGD) and recirculated seawater SGD (RSGD), to the entire Bay of Puck. Phosphate (PO43−) concentrations varied significantly among study sites and seasons, while both ammonium (NH4+) and nitrates (NO3−) concentrations varied only seasonally. The N:P ratio indicated P limitation in most of the samples. The estimated seasonal and annual loads, via SGD, of both dissolved inorganic nitrogen (DIN; 9303 t yr−1) and PO43− (950 t yr−1), were the most significant source of nutrients to the Bay of Puck, and notably higher than quantified before (FSGD nutrient loads of 50 t yr−1 and 56 t yr−1 for DIN and PO43−, respectively). The SGD fluxes reported here indicate some of the highest rates of sediment-water fluxes reported in the Baltic Sea. These results suggest that SGD (both FSGD and RSGD) should be considered as source of chemical substances to the marine environment.

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Identifying the main sources of silicate in coastal waters of the Southern Gulf of Valencia (Western Mediterranean Sea)

Sospedra J., Niencheski L. F. H., Falco S., Andrade C. F. F., Attisano K. K., Rodilla M.

Oceanologia

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2018

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No. 60 (1)

52--64

EN

Silicon is a major nutrient for siliceous primary producers, which can become a potential limiting nutrient in oligotrophic areas. Most of the silicon inputs to the marine environment come from continental discharges, from both superficial and ground waters. This study analyses the main sources of silicon and their dynamics along the southernmost 43 km of shoreline in the Gulf of Valencia (Western Mediterranean Sea). The salinity and silicate concentration in the different compartments (springs, freshwater wells, beach groundwater, surf zone and coastal waters) in this coastal area were determined. In addition, chlorophyll a and phytoplankton community were analyzed in the surf zone and coastal waters. Silicate concentrations in freshwater wells ranged between 130 and 150 μM, whereas concentrations of this nutrient declined to 49 μM in freshwater-seawater mixture transects. At the same time, there was a positive gradient in silicate for both freshwater and coastal waters southward. An amount of 18.7 t of dissolved silicate was estimated in the nearest first kilometre nearest to the coastline, 6 t of this silicate belonged to the background sea level. On the other hand, the sum of the main rivers in the area supplies 1.6 t of dissolved silicate per day. This implies that a large amount of the remaining 11.1 t must derive from submarine groundwater discharges, which would thus represent 59% of the coastal dissolved silicate budget. Overall, it is suggested that a subterranean transport pathway must contribute considerably to silicate concentrations throughout this zone, which is characterized as permeable.

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Bezpośrednie pomiary podmorskiego zasilania wodami podziemnymi Zatoki Puckiej

Bublijewska E., Łęczyński L., Marciniak M., Chudziak Ł., Kłostowska Ż., Zarzeczańska D.

Przegląd Geologiczny

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2017

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Vol. 65, nr 11/2

1173--1178

EN

Fresh water accumulated beneath the sea floor may flow through sediments into the sea water. This process, opposite to infiltration, is called Submarine Groundwater Discharge (SGD). The Southern Baltic Sea coastal zone represents an interesting object of study because its bottom deposits show seepages of fresh groundwater. The study involved Puck Bay and the adjacent coastal belt of the Kashubian Coast plateau. Research of potential outflows of fresh groundwater was done through a thermal imaging of the study area. An articulate thermal anomaly allowed predetermining the location of research points. Groundwater outflows in the seabed were confirmed by measurements of chloride content and electrical conductivity of water samples. The paper presents two new devices: a filtrometer that enables measurement of water filtration intensity during drainage, and a gradientmeter that measures the hydraulic gradient. The use of both devices allows determination of the in situ hydraulic conductivity. Results of the research have shown relationships between fresh groundwater and the sea-bottom sediments.

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Groundwater conditions along the seawater/freshwater interface on a volcanic island and a depositional area in Japan

Marui A.

Geological Quarterly

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2003

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Vol. 47, No 4

381-388

EN

Fresh groundwater comes in contact with seawater at the downstream end of its flow system. Most previous work has discussed the shape of the seawater/freshwater interface on the basis of Ghyben-Herzberg’s law. The groundwater, however, pushes the seawater farther offshore side than predicted by the law, giving rise to freshwater flows even below the bottom of the sea. A previous study found that the distribution of submarine groundwater discharge and the point of the seawater/freshwater interface on the marine floor are closely related. The cross-sectional shape of the interface onshore is clarified by using electrical tomography and observation of groundwater and soil samples taken from observation wells located in the coastal area (by a volcanic island and associated deposits). In both fields, diving was carried out to find the submarine groundwater discharge on the sea-floor and to take water samples. From the analysis of the water discharged on the marine floor and/or electric conductivity measurements in the marine sands, it is shown the freshwater flows (discharges) along the interface, even in the submarine deposits. The understanding of groundwater flows at the downstream end of the groundwater flow system (from mountainous to marine) will facilitate the development of water resources and the evaluation of environments.