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Changes in the water quality by the riverbank filtration (RBF) process were investigated in the field-scale demonstration sites. The overall water quality was improved by RBF, but Fe2+ concentration significantly increased in the riverbank-filtered water more than in the river water. This result would be caused by the interaction between the iron minerals and the river water in the aquifer and the influx of the hinterland groundwater into RBF wells. Dissolution properties of iron from the aquifer soils cored at the sites were evaluated through incubation experiment considering various values of redox potential (Eh), dissolved oxygen (DO), and hydrogen-ion concentration exponent (pH). These results presented that at the incubator with the final Eh of 470 mV, DO of 3.4, and pH of 4.53, the iron from the aquifer soil was most dissolved, and the pyrite and siderite contents in the aquifer soil decreased significantly from 11.5 to 6.22% and from 50.8 to 24.5%, respectively. Based on changes of ion concentrations (such as Fe2+, Fe3+, SO42− and NO3−) and iron species in the incubators, it was believed that pyrite and siderite minerals in the aquifer soils cause an increase in the Fe2+ concentration with the absence of DO and an increase in the Fe2+ and Fe3+ concentrations with the presence of DO. The dissolution rates of iron minerals into Fe2+ and Fe3+ were dependent on Eh, pH, and DO and were more sensitive to Eh and pH than DO. The results of this study can provide information on RBF site selection and its operation.
Jun-Young Ahn; Inseong Hwang; Namsik Park; Sung-Hyuk Park. Laboratory and field study on changes in water quality and increase in dissolved iron during riverbank filtration. Environmental Science and Pollution Research 2021, 1 -11.
AMA StyleJun-Young Ahn, Inseong Hwang, Namsik Park, Sung-Hyuk Park. Laboratory and field study on changes in water quality and increase in dissolved iron during riverbank filtration. Environmental Science and Pollution Research. 2021; ():1-11.
Chicago/Turabian StyleJun-Young Ahn; Inseong Hwang; Namsik Park; Sung-Hyuk Park. 2021. "Laboratory and field study on changes in water quality and increase in dissolved iron during riverbank filtration." Environmental Science and Pollution Research , no. : 1-11.
Processes in coastal aquifers involving variable-density fluids are often investigated using laboratory sand tanks. However, experimental monitoring of the interface between liquids of different densities is challenging, typically requiring dye tracers and photographic analysis. These are susceptible to problems of tracer adsorption and image inhomogeneity, and experiments are often limited to two-dimensional cross-sections. In addition, the water-table position is an important factor, but its accurate measurement is often difficult. A device has been developed for sand-tank experiments to obtain high-frequency, high-precision measurements of both the freshwater–saltwater interface (inferred from density) and the water-table depth, using a float and a laser sensor in a monitoring well. The proposed device was tested using a two-column experiment, allowing for the estimation of measurement errors, which were generally less than 1 mm. The measurement device can be modified to allow for the monitoring of multiple salinity values, and is well suited to sand-box experiments where salinity dynamics are otherwise difficult to visualize.
Byunghee Nam; Adrian D. Werner; Namsik Park. Float-laser device for measuring the water table and freshwater–saltwater interface in laboratory-scale experimental systems. Hydrogeology Journal 2020, 29, 909 -918.
AMA StyleByunghee Nam, Adrian D. Werner, Namsik Park. Float-laser device for measuring the water table and freshwater–saltwater interface in laboratory-scale experimental systems. Hydrogeology Journal. 2020; 29 (2):909-918.
Chicago/Turabian StyleByunghee Nam; Adrian D. Werner; Namsik Park. 2020. "Float-laser device for measuring the water table and freshwater–saltwater interface in laboratory-scale experimental systems." Hydrogeology Journal 29, no. 2: 909-918.
Salinization of the freshwater lens and well fields under future climate and groundwater demands threaten the sustainability of groundwater abstraction in small islands. In this paper, two simple indices are proposed for a comprehensive assessment of freshwater salinization in small islands. Values of these indices are computed based on a sharp-interface finite element numerical model with the interface matched to the lower limit of freshwater. The first index relates rainfall percentiles with the computed freshwater volume and provides regional assessment of changes in the volume stored in the freshwater lens over time. The second is a sustainability index, based on computed saltwater ratios in pumping wells as the performance indicator, which represents the well salinization risk at a spatial scale. The proposed methodology is illustrated with the example of Tongatapu Island. Freshwater lens dynamics and well salinization under various scenarios of dry, median, and wet general circulation model predictions-based unsteady recharge, sea level rise, and pumping demands were evaluated for the period 2010–2099. The freshwater lens of Tongatapu is dependent on rainfall, and the 60-month rainfall percentile is highly correlated with the total freshwater volume. Public well field indicates sustainability indexes of 45% and 100% under the current pumping conditions for the driest and the wettest scenarios, and with increased pumping and sea level rise, they reduce to 30% and 90%, respectively. Thus, management of pumping rates is essential for future freshwater sustainability. This methodology can be used for first-hand temporal and spatial estimations of small island freshwater lens salinization considering both the regional and well scales.
Roshina Babu; Namsik Park; Byunghee Nam. Regional and well-scale indicators for assessing the sustainability of small island fresh groundwater lenses under future climate conditions. Environmental Earth Sciences 2020, 79, 47 .
AMA StyleRoshina Babu, Namsik Park, Byunghee Nam. Regional and well-scale indicators for assessing the sustainability of small island fresh groundwater lenses under future climate conditions. Environmental Earth Sciences. 2020; 79 (1):47.
Chicago/Turabian StyleRoshina Babu; Namsik Park; Byunghee Nam. 2020. "Regional and well-scale indicators for assessing the sustainability of small island fresh groundwater lenses under future climate conditions." Environmental Earth Sciences 79, no. 1: 47.
Sustainable management of small island freshwater resources requires an understanding of the extent of freshwater lens and local effects of pumping. In this study, a methodology based on a sharp interface approach is developed for regional and well scale modeling of island freshwater lens. A quasi-three-dimensional finite element model is calibrated with freshwater thickness where the interface is matched to the lower limit of the freshwater lens. Tongatapu Island serves as a case study where saltwater intrusion and well salinization for the current state and six long-term stress scenarios of reduced recharge and increased groundwater pumping are predicted. Though no wells are salinized currently, more than 50% of public wells are salinized for 40% decreased recharge or increased groundwater pumping at 8% of average annual recharge. Risk of salinization for each well depends on the distance from the center of the well field and distance from the lagoon. Saltwater intrusions could occur at less than 50% of the previous estimates of sustainable groundwater pumping where local pumping was not considered. This study demonstrates the application of a sharp interface groundwater model for real-world small islands when dispersion models are challenging to be implemented due to insufficient data or computational resources.
Roshina Babu; Namsik Park; Sunkwon Yoon; Taaniela Kula. Sharp Interface Approach for Regional and Well Scale Modeling of Small Island Freshwater Lens: Tongatapu Island. Water 2018, 10, 1636 .
AMA StyleRoshina Babu, Namsik Park, Sunkwon Yoon, Taaniela Kula. Sharp Interface Approach for Regional and Well Scale Modeling of Small Island Freshwater Lens: Tongatapu Island. Water. 2018; 10 (11):1636.
Chicago/Turabian StyleRoshina Babu; Namsik Park; Sunkwon Yoon; Taaniela Kula. 2018. "Sharp Interface Approach for Regional and Well Scale Modeling of Small Island Freshwater Lens: Tongatapu Island." Water 10, no. 11: 1636.
Namsik Park; Chi Woong Jang; Roshina Babu. Development of minimum-salinity feedwater for reduction of unit production cost of reverse-osmosis desalination plants. Journal of Korea Water Resources Association 2016, 49, 431 -438.
AMA StyleNamsik Park, Chi Woong Jang, Roshina Babu. Development of minimum-salinity feedwater for reduction of unit production cost of reverse-osmosis desalination plants. Journal of Korea Water Resources Association. 2016; 49 (5):431-438.
Chicago/Turabian StyleNamsik Park; Chi Woong Jang; Roshina Babu. 2016. "Development of minimum-salinity feedwater for reduction of unit production cost of reverse-osmosis desalination plants." Journal of Korea Water Resources Association 49, no. 5: 431-438.
Both fresh and saline groundwater may be of some value to coastal communities. A comprehensive simulation-optimization model was developed to identify optimal solutions for managing both types of groundwater in coastal areas. The model may be used for conventional management problems of fresh groundwater development and of seawater intrusion control. In addition, the model can be used for problems of concurrent development of fresh and saline/brackish groundwater for beneficial uses. A set of hypothetical examples is given to demonstrate the applicability of the proposed model. In the protection of an over-exploiting freshwater pumping well, the saltwater pumping scheme was less efficient than the freshwater injection scheme. Although the former scheme may be more advantageous in some limited cases, the latter should be considered first as it retains more freshwater in the aquifer. The example of the concurrent development of fresh and brackish groundwater exhibited two different sets of optimal solutions: one with a large amount of freshwater and a small amount of brackish water with high salinity, and the other with a small amount of freshwater and a large amount of brackish water with low salinity. L’eau souterraine douce tout comme salée peut représenter une certaine valeur pour les communautés côtières. Un modèle complet de simulation et d’optimisation a été développé pour identifier les solutions optimales pour gérer les deux types d’eau souterraine dans les zones côtières. Le modèle peut être utilisé pour les problèmes classiques de gestion d’eau souterraine douce et de contrôle de l’intrusion d’eau de mer. En outre, le modèle peut être utilisé pour les problèmes d’exploitation concurrentielle d’eau souterraine douce et salée/saumâtre à des fins bénéfiques. Un ensemble d’exemples hypothétiques est donné pour démontrer l’applicabilité du modèle proposé. Dans le cas de la protection d’un puits de pompage surexploitant l’eau douce, un scénario de pompage d’eau salée était moins efficace qu’un scénario d’injection d’eau douce. Bien que le scénario précédent peut être plus avantageux dans certains cas limités, le dernier devrait être considéré en premier du fait qu’il favorise la conservation de l’eau douce dans l’aquifère. L’exemple d’une exploitation concurrentielle d’eaux souterraines douces et saumâtres présentait deux ensembles différents de solutions optimales : une avec un grand volume d’eau douce et un faible volume d’eau saumâtre avec une forte salinité, et l’autre avec un faible volume d’eau douce et un grand volume d’eau saumâtre avec une faible salinité. Tanto el agua subterránea dulce como la salada pueden tener algún valor para las comunidades costeras. Se desarrolló un modelo comprensivo de simulación-optimización para identificar soluciones óptimas para la gestión de ambos tipos de aguas subterráneas en las zonas costeras. El modelo puede ser usado para problemas convencionales de manejo de agua subterránea dulce y de control de la intrusión de agua de mar. Además el modelo puede ser usado para problemas de desarrollo concurrente de agua subterránea dulce y salina / salobre para usos útiles. Se da un conjunto de ejemplos hipotéticos para demostrar la aplicabilidad del modelo propuesto. En la protección de un pozo de bombeo de agua dulce sobreexplotado, el esquema de bombeo de agua salada fue menos eficiente que el esquema de inyección de agua dulce. A pesar de que el primer esquema puede tener más ventajas en algunos casos limitados, este último debiera ser considerado primeramente, ya que retiene más agua dulce en el acuífero. El ejemplo del desarrollo concurrente de agua subterránea dulce y salobre exhibió dos diferentes conjuntos de soluciones óptimas: uno con una gran cantidad de agua dulce y una pequeña cantidad de agua salobre con alta salinidad, y el otro con una pequeña cantidad de agua dulce y una gran cantidad de agua salobre con baja salinidad. 地下淡水和咸水对沿海地区的社区可能具有一定的价值。开发了一个综合模拟-最优化模型以确定管理沿海地区这两种类型地下水的最佳方法。模型可用于解决地下淡水开发及咸水入侵控制的常规管理问题。另外,模型还可以用于解决地下淡水及咸水/微咸水同时开发利用出现的问题。本文列出了一组假设的例子以展示所述模型的适用性。在保护超采的淡水抽水井过程中,咸水抽水方案不如淡水注入方案效率高。尽管前者方案在一些有限制的情况下可能更有利,但后者方案应当首先给予考虑,因为此方案在含水层中保留了更多的淡水。地下淡水和咸水同时开采的例子展示出两种不同的最佳解决方法:一种是开采大量的淡水和开采少量的高盐度微咸水,另一种是开采少量的淡水和大量的低盐度微咸水。 Ambas águas subterrâneas, doces e salgadas, podem ser de elevada importância para comunidades costeiras. Um modelo abrangente de simulação-otimização foi desenvolvido para identificar soluções ótimas para o gerenciamento de ambos os tipos de agua subterrânea nestas regiões. Este modelo pode ser utilizado para o gerenciamento de problemas típicos de desenvolvimento de recursos hídricos subterrâneos e controle de intrusão de agua salina. Adicionalmente, o modelo pode ser utilizado para problemas de uso concomitante de água doce e salgada para uso proveitoso. Uma série de situações hipotéticas são apresentados para demonstrar a aplicabilidade do modelo proposto. No caso da proteção de um poço de água doce superexplorado, o método de bombeamento de água salina se mostrou menos eficiente do que o método de injeção de água doce. Apesar de o último ser mais vantajoso em alguns casos, o primeiro deveria ser considerado como primeira opção, uma vez que...
Namsik Park; Lei Shi. A comprehensive sharp-interface simulation-optimization model for fresh and saline groundwater management in coastal areas. Hydrogeology Journal 2015, 23, 1195 -1204.
AMA StyleNamsik Park, Lei Shi. A comprehensive sharp-interface simulation-optimization model for fresh and saline groundwater management in coastal areas. Hydrogeology Journal. 2015; 23 (6):1195-1204.
Chicago/Turabian StyleNamsik Park; Lei Shi. 2015. "A comprehensive sharp-interface simulation-optimization model for fresh and saline groundwater management in coastal areas." Hydrogeology Journal 23, no. 6: 1195-1204.