The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Jörg Imberger - One of the best experts on this subject based on the ideXlab platform.
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the influence of physical and physiological processes on the spatial heterogeneity of a microcystis bloom in a Stratified Reservoir
Ecological Modelling, 2014Co-Authors: Sewoong Chung, Jörg Imberger, Matthew R HipseyAbstract:A three-dimensional coupled hydrodynamic and ecological model, ELCOM–CAEDYM, was extended to include buoyancy control dynamics for cyanobacteria, and validated in the Stratified Daecheong Reservoir (Korea). Specifically, the model was used to explore the physical and biological processes that determined the temporal and spatial variability of Microcystis aeruginosa (hereafter Microcystis) biomass during an abnormally intense mono-specific bloom event. Inclusion of the buoyancy control function within the coupled model considerably improved the model predictability by capturing the biomass accumulation at the surface during the bloom, and the shift of the dominant group from green algae to cyanobacteria. Results indicated that physical processes, particularly inflow mixing, played a dominant role in determining the spatial heterogeneity of Microcystis biomass through the local control of nutrient availability. In addition, the shallow mixed layer depth (zm) relative to the euphotic depth (zp) under a stable thermal stratification provided a perfect physical habitat for the dominance of this cyanobacteria relative to other species, due to their buoyancy control capability. This work demonstrates that the coupled hydrodynamic and ecological modeling has advanced to a stage where it may be used to interpret field data and subject to a suitable level of validation, the model may be used as a management decision support tool.
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pathways of multiple inflows into a Stratified Reservoir thomson Reservoir australia
Advances in Water Resources, 2011Co-Authors: Clelia L Marti, Rianda Mills, Jörg ImbergerAbstract:The interaction of multiple inflows entering a Reservoir (Thomson Reservoir, Australia) is investigated with a field experiment and three-dimensional numerical model simulations. The focus of the study is the mixing and transport patterns within the Reservoir of the inflowing water. Data from the field experiment showed the existence of multiple inflows intruding horizontally into the Reservoir immediately below the thermocline and selectively propagating into the Reservoir at a depth determined by the individual density of each inflow. The results serve to show that inflows slot into a Stratified Reservoir in an orderly fashion, their depth dependent on the separation of inflow densities and Reservoir bed, with minimal mixing between intrusions. Inflows thus do not take their nutrient load into the Reservoir as a whole, but rather slot their load into an intrusion layer at an appropriate depth. Nutrients brought in via inflows become accessible only when vertical mixing, either directly at the base of the surface layer, or indirectly via the benthic boundary layer flux, transports the intrusion waters into the surface layer.
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spatial distribution of motile phytoplankton in a Stratified Reservoir the physical controls on patch formation
Journal of Plankton Research, 2008Co-Authors: Ryan Alexander, Jörg ImbergerAbstract:Changes in the spatial distribution of the dinoflagellate Ceratium hirundinella were observed in a Stratified, medium-sized (16 km 2 ) Argentinean Reservoir over several days. A fluorescence profiling technique was used to identify persistent patchiness in the distribution of the dinoflagellate. A three-dimensional numerical model was used to reconcile a range of different unsteady processes and prove that the initial source of heterogeneity in the system was the vertical migration of Ceratium. Once migration established vertical heterogeneity, the dominant influence on the patch dynamics alternated between control by migration and control by mixing and transport. This led to the development of persistent horizontal patchiness. The analysis revealed that the region of the lake inhabited by Ceratium was highly predictable and from this result it was determined that physical processes (with some influence from migration) control the habitat of this dinoflagellate rather than biological/chemical gradients. When the spatial habitat of a particular phytoplankton species can be isolated in this manner, the resources available to the species can be more accurately determined by further study. The results are particularly applicable to the study of motile/buoyant plankton in aquatic systems that are periodically subject to moderate or strong wind forcing events.
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dissolved oxygen response to wind inflow interactions in a Stratified Reservoir
Limnology and Oceanography, 2007Co-Authors: Daniel A Botelho, Jörg ImbergerAbstract:Results of a field campaign and numerical simulations are used to show how physical mechanisms impose length scales and timescales that determine the dominant biogeochemical process. As an example, the dynamics of the Snake River inflows into Brownlee Reservoir is investigated to explain the onset and maintenance of an oxygen-depleted region (the oxygen block) in the surface layer of the upstream part of the Reservoir. The oxygen block was located in a region of the Reservoir in which the surface layer was warmer as a result of smaller wind stresses and reduced evaporation rates. Numerical simulations reproduced the hydrodynamic field observations resulting from inflow, outflow, wind stress, and atmospheric heat fluxes. When the wind stress opposed the inflow, the surface layer was arrested, forming a zone of convergence, stagnating the fluid and allowing the biological oxygen demand in the water to deplete the dissolved oxygen (DO) in the surface water; direct measurements showed that vertical mixing was small and contributed only marginally to the oxygen depletion. Net DO production in the water column was consistent with the observed variation with the buoyant inflow pattern, that is, a sink during overflows and overcast days and a source during interflows and intense sunlight. These observations provided further evidence that the water in this region was biologically isolated as confirmed by a scaling analysis. Modern numerical hydrodynamic simulations have reached a level of accuracy where they may be used to identify and quantify ecological niches.
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effect of long internal waves on the quality of water withdrawn from a Stratified Reservoir
Journal of Hydraulic Engineering, 2006Co-Authors: Vadim V Anohin, Jörg Imberger, Jose R Romero, Gregory IveyAbstract:The properties of water withdrawn from a Stratified Reservoir are investigated in a field study conducted in Lake Burragorang, Australia. It is shown that temperature and turbidity fluctuations of the extracted water are directly correlated to the vertical displacement of the thermal structure of the Reservoir immediately in front of the offtake and the thickness of the selective withdrawal layer. Scaling of the unsteady withdrawal revealed that the timescale associated with the formation of selective withdrawal is an order of magnitude smaller than the typical period of the internal wave. This means the withdrawal layer is acting as a filter, extracting water of a particular quality as it is swept past the outlet by the internal seiches; the steady-state theory of the selective withdrawal can be used to predict outflow temperature fluctuations in Reservoirs where long internal waves are present. To correctly interpret other outflow water parameters, such as turbidity or dissolved oxygen, it is important ...
Tinglin Huang - One of the best experts on this subject based on the ideXlab platform.
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inducing an extended naturally complete mixing period in a Stratified Reservoir via artificial destratification
Science of The Total Environment, 2020Co-Authors: Nan Li, Tinglin Huang, Yang Li, Fan Si, Haihan ZhangAbstract:Naturally complete mixing (i.e., ΔT <1 °C across the entire water column) driven by convection in winter is an ideal state for maintaining good water quality, as it spontaneously redistributes dissolved oxygen (DO) over the entire water column and prevents hypolimnetic anoxia and associated pollution. A complete mixing duration is quite short under natural mixing conditions, whereas artificial destratification systems can artificially induce an earlier occurrence of complete mixing, thereby prolonging the span of the naturally complete mixing period by several months. Based on multi-year in situ water quality measurements and meteorological data during natural and artificial mixing periods, this study evaluates the effects of water-lifting aerators (WLAs) and climatic factors on convective mixing processes and their duration. WLA-supplied turbulent kinetic energy (TKE) and WLA-induced hypolimnion warming significantly decrease the water stability and extend the naturally complete mixing period for 2.6-fold. The results indicate that an optimal WLA implementation should immediately achieve complete mixing when surface mixing occurs in autumn. By evaluating the influence of WLAs and other factors on convective mixing, this study provides insights for successful destratification system operations (i.e., WLAs) to replenish oxygen concentrations across the water column and minimize operating costs by taking advantage of climatic conditions. Although our study focuses on WLA-induced mixing, these observations can be applicable to other destratification systems in most of the Stratified Reservoirs and lakes.
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Inducing an extended naturally complete mixing period in a Stratified Reservoir via artificial destratification.
Science of The Total Environment, 2020Co-Authors: Nan Li, Tinglin Huang, Yang Li, Fan Si, Haihan ZhangAbstract:Naturally complete mixing (i.e., ΔT
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water quality and bacterial population driving mechanism of algae vertical succession in Stratified Reservoir
Huan jing ke xue= Huanjing kexue, 2020Co-Authors: Shengnan Chen, Tinglin Huang, Yutian Miao, Rongrong ZongAbstract:Phytoplankton and bacteria are important components of the aquatic food web, and play a critical role in substance circulation and energy exchange in freshwater ecosystems. The succession of algae is closely related to the metabolism and structural succession of bacterial populations in the water column. Thus, in this study, the vertical succession characteristics of phytoplankton and bacteria community structure and their coupling with water quality were investigated during an algal bloom in the Lijiahe Reservoir using high-throughput DNA sequencing and Biolog technologies. The results showed that the Lijiahe Reservoir was in the thermal stratification stage in August, and the pH, dissolved oxygen, and NH4+-N of the water column gradually decreased with depth (P<0.001). Algal cell concentration and chlorophyll a exhibited a simultaneous trend (P<0.001), and the maximum values in the surface layer were 3363.33×104 cells·L-1 and 7.03 μg·L-1, respectively. The algal community structure was dominated by Microcystis at water depths of 0 m and 3 m, and at 6 m water depth, Cyclotella replaced Microcystis as the most dominant algae, with a relative abundance of 57.28%. Biolog analysis indicated that the outbreak of Microcystis had a significant impact on bacterial metabolic activity and its relative abundance, but the diversity of bacterial population metabolic activity varied less. A total of 1420 operational taxonomic units were found by high-throughput sequencing, belonging to 10 bacterial phyla. Of these, Actinobacteria and Proteobacteria dominated in all water layers, and their relative abundances were more than 50%. The relative abundance of Chlorobi and Planctomycetes varied significantly with water depth, reaching their maxima at a depth of 6 m with values of 10.29% and 6.78%, respectively, which were both negatively correlated with algal density (P<0.05). Firmicutes and Gemmatimonadetes were positively correlated with algal density (P<0.05). A heat map fingerprint showed that the vertical distribution of the bacterial community structure of the Lijiahe Reservoir varied significantly, and with the increase in water depth, the bacterial community was more uniformly distributed and tended to diversify. Redundancy analysis (RDA) showed that the vertical distribution of the bacterial and algal community structure was regulated by different water qualities, and the difference was significant. This study investigated the coupling mechanism of algal and bacterial communities during the algal bloom in the Lijiahe Reservoir, and the results provided a scientific basis for the investigation of the molecular microecological driving mechanism of water-source algal blooms.
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spatial and temporal succession characteristics of aerobic anoxygenic photosynthesis bacteria in a Stratified Reservoir
Huan jing ke xue= Huanjing kexue, 2020Co-Authors: Haihan Zhang, Tinglin Huang, Nan Li, Fan Si, Yan Wang, Chenxu Wang, Linchao Lu, Yutian MiaoAbstract:Aerobic anoxygenic photosynthesis bacteria (AAPB) play a significant role in the material circulation of the hydrosphere, with diverse community structure and unique metabolic functions. To investigate the spatial and temporal succession characteristics of AAPB abundance and community structure in Jinpen Reservoir, a quantitative real-time polymerase chain reaction and Illumina MiSeq high-throughput sequencing technique targeting the pufM gene were applied. Furthermore, redundancy analysis was used to determine the influence of environmental factors on their community structure. The results showed that the AAPB abundance ranged from (6.70±0.43)×103 to (2.69±0.15)×104 copies·mL-1, with the maximum value appearing in October, and decreased with an increase in water depth. Samples were mainly classified into 19 genera (except for the unclassified genus); the most abundant AAPB genera were Bradyrhizobium sp. and Methylobacterium sp., which were affiliated to the α-Proteobacteria, and the proportion of the Bradyrhizobium sp. was highest in November, accounting for more than 60% (except 10 m). Furthermore, Rubrivivax sp., belonging to β-Proteobacteria, was found to have a low proportion. There was a strong interaction relationship between AAPB genera. For example, Rhodobacter sp. was positively correlated with Rhodovulum sp., while Hydrogenophaga sp. was negatively correlated with Bradyrhizobium sp.. The community structure composition and distribution of AAPB were significantly different, mainly affected by temperature (T), total nitrogen (TN), NO3--N, and light intensity and comprehensively regulated by environmental factors. For instance, T, TN, and total phosphorus had a significant impact on the AAPB community structure of water samples at 0, 5, and 15 m in October, whereas light intensity, pH, DO, and chlorophyll-a were major structuring factors in the AAPB assemblages of water samples at 5 m in December. The results have guiding significance for parsing the spatial and temporal variability of AAPB abundance and diversity in Stratified Reservoirs, and simultaneously provide a theoretical basis for exploring the driving factors of AAPB population structure.
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response of the water quality of a Stratified Reservoir to an extreme el nino event during summer
Huan jing ke xue= Huanjing kexue, 2017Co-Authors: Tinglin Huang, Mingzheng ZengAbstract:: Global warming can intensify the El Nino phenomenon that recurs every 2-7 years, which will lead to a great interannual variability of climate and may induce the deterioration of the water quality of Reservoirs. To study the influence of the extreme El Nino events on the water quality of Stratified Reservoirs during summer, field surveys were conducted in Zhoucun Reservoir and its inflow rivers from May to August in a normal year (2012) and a strong El Nino year (2015). Temporal variations of physical and chemical index were investigated during monitoring. The results showed that the Zhoucun Reservoir was Stratified during the study period. The precipitation in the summer of the normal year was significantly higher than that in the El Nino year at the same period. In the summer of the normal year, the water level increased from 124.26 m to 127.14 m and the hypolimnion thickness increased by 3.1 m. However, in 2015, the rapid decrease of the water level from May to August (from 121.65 m to 119.46 m) led to the decrease of the hypolimnion thickness (by 3.2 m). The inflow rivers belonged to surface current and its nutrients concentrations were obviously higher than those in the epilimnion. The inflow nutrients loads increased significantly in the summer of the normal year, as a result, total nitrogen increased from 1.00 mg·L-1 to 2.06 mg·L-1, nitrate increased from 0.19 mg·L-1 to 1.28 mg·L-1, and total phosphorus increased from 0.023 mg·L-1 to 0.088 mg·L-1 in the lacustrine zone of the Reservoir. In contrast, the nutrients concentrations changed little in the summer of the El Nino year due to the decrease in runoff. Nonetheless, the reducing pollutants concentrations of the hypolimnion in the El Nino year were significantly higher than those in the normal year, which may be due to the temporal variations of hypolimnion thicknesses. The maximum concentrations of iron, manganese, ammonium and sulfide in the summer of the El Nino year were 0.38, 1.36, 2.36 and 1.67 mg·L-1, respectively. All these index exceeded the standards for surface water Class Ⅲ. We conclude that the extreme El Nino event has an apparent influence on the nutrients concentrations in the epilimnion and the pollutants concentrations in the hypolimnion in Zhoucun Reservoir.
Wei He - One of the best experts on this subject based on the ideXlab platform.
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effects of temperature control curtain on algae biomass and dissolved oxygen in a large Stratified Reservoir sanbanxi Reservoir case study
Journal of Environmental Management, 2019Co-Authors: Wei He, Linghang Xing, Xiaodong Yu, Jian Zhang, Sheng ChenAbstract:: A temperature-control curtain (TCC) is a new technique of selective withdrawal for controlling the outflow temperature of a Reservoir. A TCC can significantly affect the Reservoir hydrodynamic and thermal structure, but its effects on water quality and ecology remain unknown. In this study, we developed and calibrated a hydro-thermal-water quality model to numerically analyze how a TCC located 1 km from a dam affected algal biomass and water quality in a Reservoir. According to our results, when a TCC was used, the mean annual chlorophyll a (Chl-a) concentrations in the Reservoir decreased. Chl-a concentrations remained constant during the heating period until normal water levels were reached, and increased during the cooling period and decreased until year-end drawdown levels were reached. The dissolved oxygen (DO) concentrations decreased and the anoxic proportions increased throughout the year. The yearly mean Chl-a and DO concentrations in the Reservoir declined continuously as the water-retaining proportion (Pr) of the TCC increased from 0 to 87.5%, while the anoxic proportion (DO < 2 mg/L) first increased and then decreased, peaking at a Pr of 62.5%. The change patterns of the anoxic proportion were consistent with those of thermal stability, demonstrating the applicability of thermal stability in predicting Reservoir hypoxia. Moreover, the environmental impact of TCCs will increase under global warming, and TCCs can mitigate the increased algal biomass and further decrease DO in warmer climate conditions. Under a medium-high climate scenario, Representative Concentration Pathway 6.0, and a TCC having 75% Pr, the yearly mean Chl-a, DO concentrations, and anoxic proportions of Sanbanxi Reservoir are predicted to reach 10.7 μg/L, 4.2 mg/L, and 39.6%, respectively, by 2046-2065. Thus, changes in the water environment and ecology (particularly the likely deterioration of water quality because of selective withdrawal under global warming) should be considered as a component of water management practices.
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analysis of the thrust force on the temperature control curtain in a large Stratified Reservoir
Journal of Hydraulic Engineering, 2017Co-Authors: Wei He, Jijian Lian, Mudan WuAbstract:AbstractA temperature-control curtain (TCC) is an effective facility to regulate the outflow temperature in Reservoirs, and its safety and stability are of great concern. The pressure difference be...
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modeling the effect of temperature control curtain on the thermal structure in a deep Stratified Reservoir
Journal of Environmental Management, 2017Co-Authors: Wei He, Jijian Lian, Mudan WuAbstract:Abstract Temperature-control curtain (TCC) is an effective facility of selective withdrawal. Previous research has estimated the influence of TCC on the outflow temperature, but its effect on the thermal structure of a Reservoir area is unknown, which is crucial to the Reservoir ecology. For this purpose, taking the Sanbanxi Reservoir as a case study, a 2-D hydrodynamic and temperature model covering the whole Reservoir was built and calibrated to simulate the flow and temperature fields under different TCC scenarios, and the change rules of thermal stability and outflow temperature are obtained. When the water-retaining proportion ( P r ) of bottom-TCC increases, the temperature difference between inflow and outflow monotonously decreases, while the thermal stability first increases and later decreases. The maximum thermal stability exists at P r = 62.5%; it goes against water quality improvement and should be avoided in practice. A bottom-TCC with P r > 80% is practical for deep Reservoirs such as Sanbanxi Reservoir to decrease the temperature difference between inflow and outflow without the increase of thermal stability. In terms of top-TCC, as P r increases, the temperature difference between inflow and outflow monotonously increases and thermal stability decreases. The top-TCCs are recommended when a smaller thermal stability is more preferentially considered than outflow temperature, or a cool outflow in the summer is required for downstream coldwater fishes. In addition, the TCC cannot decrease or increase the outflow temperature all of the time throughout the whole year, and it primarily changes the phase and variation range of the outflow temperature. This study quantitatively estimates the potential effect of TCCs on the thermal structure and water environment management and provides a theoretical basis for the application of TCC.
Mudan Wu - One of the best experts on this subject based on the ideXlab platform.
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analysis of the thrust force on the temperature control curtain in a large Stratified Reservoir
Journal of Hydraulic Engineering, 2017Co-Authors: Wei He, Jijian Lian, Mudan WuAbstract:AbstractA temperature-control curtain (TCC) is an effective facility to regulate the outflow temperature in Reservoirs, and its safety and stability are of great concern. The pressure difference be...
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modeling the effect of temperature control curtain on the thermal structure in a deep Stratified Reservoir
Journal of Environmental Management, 2017Co-Authors: Wei He, Jijian Lian, Mudan WuAbstract:Abstract Temperature-control curtain (TCC) is an effective facility of selective withdrawal. Previous research has estimated the influence of TCC on the outflow temperature, but its effect on the thermal structure of a Reservoir area is unknown, which is crucial to the Reservoir ecology. For this purpose, taking the Sanbanxi Reservoir as a case study, a 2-D hydrodynamic and temperature model covering the whole Reservoir was built and calibrated to simulate the flow and temperature fields under different TCC scenarios, and the change rules of thermal stability and outflow temperature are obtained. When the water-retaining proportion ( P r ) of bottom-TCC increases, the temperature difference between inflow and outflow monotonously decreases, while the thermal stability first increases and later decreases. The maximum thermal stability exists at P r = 62.5%; it goes against water quality improvement and should be avoided in practice. A bottom-TCC with P r > 80% is practical for deep Reservoirs such as Sanbanxi Reservoir to decrease the temperature difference between inflow and outflow without the increase of thermal stability. In terms of top-TCC, as P r increases, the temperature difference between inflow and outflow monotonously increases and thermal stability decreases. The top-TCCs are recommended when a smaller thermal stability is more preferentially considered than outflow temperature, or a cool outflow in the summer is required for downstream coldwater fishes. In addition, the TCC cannot decrease or increase the outflow temperature all of the time throughout the whole year, and it primarily changes the phase and variation range of the outflow temperature. This study quantitatively estimates the potential effect of TCCs on the thermal structure and water environment management and provides a theoretical basis for the application of TCC.
Sewoong Chung - One of the best experts on this subject based on the ideXlab platform.
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pCO2 Dynamics of Stratified Reservoir in Temperate Zone and CO2 Pulse Emissions During Turnover Events
Water, 2018Co-Authors: Hyungseok Park, Sewoong ChungAbstract:This study explores the dynamic changes in the partial pressure of CO2 (pCO2) with depth, and the temporal variations of CO2 net atmospheric flux (NAF) in a Stratified Reservoir. A total of 16 field campaigns were conducted from the summer stratification to fall turnover period in 2017. A random forest (RF) model was developed to estimate the pCO2 using concurrently measured water quality variables. The results showed that the vertical distribution of pCO2 and associated temporal variations of the NAF are closely related to the stratification strength of the Reservoir. The Reservoir surface pCO2 was supersaturated (1542 µatm) in summer (July 11), but this decreased to undersaturation as algae grew. Meanwhile, dissolved CO2 continuously accumulated below the Reservoir mixed-layer due to the thermal stratification barrier and organic-rich floodwater intrusion. Vertical mixing began instantly as the stratification strength began to weaken in mid-October, and the surface pCO2 increased sharply up to 1934 µatm. Consequently, the NAF drastically increased to 3235 mg−CO2 m−2·day−1, which implies that the NAF changes seasonally and large CO2 pulsing occurs during the turnover events. The results provide valuable information about pCO2 variability and physical mixing processes, as well as carbon budget estimation in Stratified Reservoirs, and offer an improved understanding of these phenomena.
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the influence of physical and physiological processes on the spatial heterogeneity of a microcystis bloom in a Stratified Reservoir
Ecological Modelling, 2014Co-Authors: Sewoong Chung, Jörg Imberger, Matthew R HipseyAbstract:A three-dimensional coupled hydrodynamic and ecological model, ELCOM–CAEDYM, was extended to include buoyancy control dynamics for cyanobacteria, and validated in the Stratified Daecheong Reservoir (Korea). Specifically, the model was used to explore the physical and biological processes that determined the temporal and spatial variability of Microcystis aeruginosa (hereafter Microcystis) biomass during an abnormally intense mono-specific bloom event. Inclusion of the buoyancy control function within the coupled model considerably improved the model predictability by capturing the biomass accumulation at the surface during the bloom, and the shift of the dominant group from green algae to cyanobacteria. Results indicated that physical processes, particularly inflow mixing, played a dominant role in determining the spatial heterogeneity of Microcystis biomass through the local control of nutrient availability. In addition, the shallow mixed layer depth (zm) relative to the euphotic depth (zp) under a stable thermal stratification provided a perfect physical habitat for the dominance of this cyanobacteria relative to other species, due to their buoyancy control capability. This work demonstrates that the coupled hydrodynamic and ecological modeling has advanced to a stage where it may be used to interpret field data and subject to a suitable level of validation, the model may be used as a management decision support tool.
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characterization and modeling of turbidity density plume induced into Stratified Reservoir by flood runoffs
Water Science and Technology, 2009Co-Authors: Sewoong ChungAbstract:In monsoon climate area, turbidity flows typically induced by flood runoffs cause numerous environmental impacts such as impairment of fish habitat and river attraction, and degradation of water supply efficiency. This study was aimed to characterize the physical dynamics of turbidity plume induced into a Stratified Reservoir using field monitoring and numerical simulations, and to assess the effect of different withdrawal scenarios on the control of downstream water quality. Three different turbidity models (RUN1, RUN2, RUN3) were developed based on a two-dimensional laterally averaged hydrodynamic and transport model, and validated against field data. RUN1 assumed constant settling velocity of suspended sediment, while RUN2 estimated the settling velocity as a function of particle size, density, and water temperature to consider vertical stratification. RUN3 included a lumped first-order turbidity attenuation rate taking into account the effects of particles aggregation and degradable organic particles. RUN3 showed best performance in replicating the observed variations of in-Reservoir and release turbidity. Numerical experiments implemented to assess the effectiveness of different withdrawal depths showed that the alterations of withdrawal depth can modify the pathway and flow regimes of the turbidity plume, but its effect on the control of release water quality could be trivial.
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a two dimensional model for simulating the transport and fate of toxic chemicals in a Stratified Reservoir
Journal of Environmental Quality, 2003Co-Authors: Roy R Gu, Sewoong ChungAbstract:A two-dimensional Reservoir toxics model is essential to establishing effective water resources management and protection. In a Reservoir, the fate of a toxic chemical is closely connected with flow regimes and circulation patterns. To better understand the kinetic processes and persistence and predict the dissipation of toxic contaminants in the Reservoir during a spill or storm runoff event, a toxics submodel was developed and incorporated into an existing laterally integrated hydrodynamics and transport model. The toxics submodel describes the physical, chemical, and biological processes and predicts unsteady vertical and longitudinal distributions of a toxic chemical. The two-dimensional toxicant simulation model was applied to Shasta Reservoir in California to simulate the physico-chemical processes and fate of a volatile toxic compound, methyl isothiocyanate (MITC), during a chemical spill into the Sacramento River in 1991. The predicted MITC concentrations were compared with those observed. The effect of Reservoir flow regimes on the transport and fate of the toxic substance was investigated. The results suggested that the persistence of MITC is significantly influenced by different flow regimes. Methyl isothiocyanate is more persistent in the Reservoir under an interflow condition due to reduced volatilization from deep layers than under an overflow condition. In the overflow situation, the plume moved more slowly toward the dam and experienced greater dissipation. This analysis can assist in toxic spill control and Reservoir management, including field sampling and closure of water intakes.
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two dimensional simulations of contaminant currents in Stratified Reservoir
Journal of Hydraulic Engineering, 1998Co-Authors: Sewoong Chung, Ruochuan GuAbstract:An unsteady two-dimensional (2D) Reservoir hydrodynamics and transport model is employed to simulate contaminated density currents in the Shasta Reservoir after a chemical spill into the Sacramento River, Calif. Three flow regimes (plunging flow, underflow, and interflow) and their occurrence are captured by the laterally averaged model. Transport and mixing processes in the temperature-Stratified Reservoir are analyzed through simulations of flow velocities, water temperature, and contaminant concentration. Flow behavior of the contaminant plume is described by plunge distance, separation depth, intruding thickness, and the spatial and temporal dilution of chemicals. Simulation results are compared with field data for water temperature and contaminant concentration collected in the Reservoir during the emergency response to the spill. Relatively good agreement between field measurements and predicted Reservoir stratification and chemical dilution is obtained. It is shown that the aeration system installed in the Reservoir contributed to the downstream reduction of chemical concentration to a nondetectable level shortly after the spill. The 2D simulations and analyses improve understanding and predictions of the movement of a conservative contaminant plume in a Stratified Reservoir. The results can assist in contamination control and remediation after a toxic chemical spill, guide field sampling during the spill, and provide information useful for water quality management.