Estuary And Lake Computer Model Research Articles

A Methodology for the Estimation of Microplastic Concentration in Relation to the Meteorological Forcing and WWTPs Effluents in Urban Coastal Areas

The study of the urban coastline is of great significance for understanding the impacts of human activities on the marine environment. Only recently the emission of microplastics is starting to be considered as a threat to aquatic and terrestrial ecosystems and currently, little information on this topic is available. The present study focuses on the development of a methodology based on the implementation of the hydrodynamic circulation model ELCOM (Estuary and Lake Computer Model) for the estimation of microplastics distribution in Kavala Gulf coastline. The approach aims to include the effects of the high seasonal touristic activity and consequent large fluctuations in wastewater treatment plants (WWTPs) discharge rates. Parameters such as microplastic concentration, effluent flow rate and temperature, meteorological forcing and scalars at the boundaries were applied and the simulation was designed to cover the entire 2006 in order to include an approximation of the seasonal 3D dispersion patterns. The microplastic concentration was estimated based on the suspended particulate matter (SPM) concentration measurements applying the approach of [1]. The physical and chemical parameters of the particles were assumed to conform with the assumptions of [2]. The results showed a strong correlation between the microplastics dispersion patterns, the wind climate and the seasonal increase in population during the summer. Microplastic concentrations reached up to 0.185 μg/l in the WWTPs adjacent coastline in correspondence to the beaches with the highest touristic activity. The periodical formation of anticyclonic flows resulted in a net transport towards the center of the gulf and an increase in microplastic concentration in the bottom layer. On the other hand, the simulation showed that considerable quantities of microplastics tend to be transported outside the study area and far from the coastline in deeper waters.

Transport of municipal wastewater, industrial and tributary discharges in eastern Lake Ontario and upper St. Lawrence River during the ice-free period of 2006

Abstract The surface transport of point and non-point source discharges into eastern Lake Ontario and upper St. Lawrence River was modeled as passive tracers using the Estuary and Lake Computer Model (ELCOM) during the ice-free period of 2006. Model hydrodynamics were validated against temperature and current observations and Lagrangian drifter tracks. Root-mean-square (RMS) errors of simulated temperature profiles were comparable to other model applications; however, current RMS errors and Fourier Norms were nominally larger than in open lake applications, and RMS errors for drifter tracks were 0.5–4.0 km (3 day duration). The errors in simulating currents and drifters, relative to temperatures, are likely the result of the difficulty in representing the complex geometry of the region, which is composed of numerous channels and islands. To determine the physical processes responsible for tracer transport, cross-correlation coefficients were calculated when model processes were switched off (e.g., wind forcing, surface thermodynamics, Earth rotation, St. Lawrence River outflow, etc.). Wind was found to be the most dominant process forcing transport of tracers both in the Kingston Basin and the St. Lawrence River, whereas the St. Lawrence River outflow, controlled by the Moses Saunders Dam, was found to influence the transport of tracers along the river. Tracers were transported ~ 60 km eastward under moderate to strong winds (> 5 ms − 1 ), remained nearshore when constrained within channels or by islands and had minimum dilutions of 20% and 39% at the Kingston Central and Kingston West drinking water intakes, respectively. The results suggest that factors such as the proximity between intakes and outfalls and presence of flow constraining topography, should be considered in future source and wastewater planning.

Three dimensional modeling of the effects of changes in meteorological forcing on the thermal structure of Lake Erie

A three dimensional hydrodynamic model, the Estuary and Lake Computer Model (ELCOM), validated by field data collected in 2008, is used to investigate the thermal structure response in Lake Erie to changes in air temperature and wind speed. We define spatially and temporally varying regions for the epilimnion, thermocline, and hypolimnion. Increasing the air temperature warms up the epilimnion but has little effect on the hypolimnion. The stratification forms earlier and breaks down later. The thermocline is raised modestly in the warmer air temperature scenario. Stronger winds cool the epilimnion slightly, but warm up the hypolimnion with much larger temperature changes. The stratification duration is shortened, and the thermocline depth is noticeably deepened. Due to the large differences in depths and layer thicknesses of the three basins, the responses to changes in meteorological forcing vary among the basin. Exploiting the power of the three dimensional model to provide a more authentic characterization of thermal stratification in large lakes, it is shown that patterns inferred from simple isotherm dynamics when studying the stratification period as typically done with one dimensional models are not always accurate. The present results for Lake Erie show the potential for complicated and interactive effects of climate forcing on important biogeochemical processes, especially hypolimnetic oxygen depletion.

Internal waves and mixing in a stratified reservoir: Insights from three-dimensional modeling

In this study, the three-dimensional (3D) Estuary and Lake COmputer Model (ELCOM) was used to model a mid-sized reservoir (Rappbode Reservoir, Germany) during the period of summer stratification to identify and illustrate the source of internal waves as well as to characterize water exchange between the hypolimnion and epilimnion under different wind speed conditions with a focal point on one episode of high and sustained winds. The modeling revealed that wind stress was the key driver of the observed internal waves while the role of water withdrawal was negligible. Our results also showed that within the range of wind speeds considered, wind-induced upwelling greatly enhanced mixing between the hypolimnion and epilimnion with a rate that varies approximately as the square of the wind speed. This numerical correlation affirmed that processes connected to wind stress, i.e. internal waves or direct upwelling, were responsible for the mixing of the hypolimnetic water into the surface water rather than direct input of turbulent kinetic energy.

Summary performance of the Estuary and Lake Computer Model (ELCOM): application in the Laurentian and other Great Lakes

The use of sophisticated three-dimensional (3D) hydrodynamic models is often required to simulate the spatial and temporal variability of water quality in large lakes. Recently, coupled lake–atmosphere models have also been developed to resolve the spatial distribution of the thermal behavior in lakes and to assess the feedback mechanisms at the air–water interface. In the studies summarized in this paper, the 3D Estuary and Lake Computer Model (ELCOM) acts as the hydrodynamic driver that provides temperature, salinity, and the transport fields that, if coupled with the Computational Aquatic Ecosystem Dynamics Model (CAEDYM), simulates nutrients, phytoplankton, zooplankton, and benthic habitat. This study presents a summary of the performance of ELCOM, and in an indirect form, serves as well as a corroboration of the strength or weakness of the coupled modeling and its ability to reproduce the thermal structure and circulation patterns, with examples from the Laurentian Great Lakes (Erie and Ontario), Northern Great Lakes (Great Slave Lake and Great Bear Lake), and Lake Winnipeg in Central Canada.

Hydrodynamics of eastern Lake Ontario and the upper St. Lawrence River

Eastern Lake Ontario and the upper St. Lawrence River provide drinking water for approximately 175,000 people. To understand the flow dynamics surrounding the eight drinking water intakes in this region, the hydrodynamics were simulated using the Estuary and Lake Computer Model (ELCOM) for the period April–October 2006. Model simulated water levels, temperatures, and current velocities were compared with observations. Root-mean-square errors in temperature and current simulation were ~2°C and ~5–8cms−1, respectively. Normalized Fourier norms ranged from 0.8 to 1.2. These errors are consistent with other applications of Reynolds-averaged models to the Great Lakes. ELCOM thus reasonably captures the dynamics of the flow regimes in the nearshore region. The flow was found to be predominantly wind induced in the southwestern lacustrine portion of the domain, with observed but not modeled weak near-inertial oscillations, and hydraulically driven in the northeastern riverine portion. Diurnal and semi-diurnal forcing influenced the flow throughout the domain. Flow reversal of the St. Lawrence River near Kingston occurred during strong easterly storm events. The model results were applied to delineate Intake Protections Zones surrounding the municipal drinking water intakes.

Three-Dimensional Modeling of a Wave-Driven Seawater Pump Inflow to the Port of Ensenada, Mexico

Like most harbors, the Port of Ensenada, Mexico, is vulnerable to the accumulation of pollutants. A wave-driven seawater pump (Sistema de Bombeo por Energía de Oleaje [SIBEO]) is proposed to inject clean and oxygen-rich water from outside the Port to promote flushing in its more stagnant areas. Three-dimensional, numerical simulations with the Estuary and Lake Computer Model (ELCOM) were used to investigate the behavior, extent, and effect of the SIBEO inflow. Conservative tracer experiments indicate that the effect of the pump would spread through the pycnocline and become noticeable throughout the harbor within a month. The tracer method yields a bulk estimate of the flushing time for the port of approximately 4 days, although the spatial variability of the flushing is significant. The least-flushed areas of the harbor are its NE and SE corners, where greater concentrations of pollutants have been observed.

Including drag and inertia in drifter modelling

The influence of inertia and drag on modelled drifter movement is investigated through comparisons of field-observed drifter paths within Marmion Marine Park, Western Australia and those simulated using the Estuary and Lake Computer Model (ELCOM). Simulated drifter paths were generated with existing Lagrangian and leeway modelling techniques, as well as with the “Generalized, Acceleration-Based Inertia and Forcing” (GABI-F) model developed herein. The GABI-F drifter model predicts drifter movement by determining the forces acting on the drifter by the surrounding fluids and incorporates the influence of winds and inertia on drifter motion. Modelling results indicate the physically based GABI-F drifter modelling method is an improvement over existing Leeway and Lagrangian methods, however, the improvement is only significant when the underlying hydrodynamic model adequately resolves time/space complexities of the flow field. Quantitative model analyses are determined suitable only over short temporal and spatial scales, past which analyses of the drifter motion only provide qualitative information relating to the model's ability to reproduce the larger scale patterns of the field drifter motion.

Dynamics of the benthic boundary layer in a strongly forced stratified lake

Field data and the three-dimensional (3D) Estuary and Lake Computer Model (ELCOM) were used to investigate the impact of periodic forcing on the structure and dynamics of the benthic boundary layer (BBL) in Lake Kinneret, Israel, a large lake that experiences strong thermal stratification and wind forcing events. Microstructure data were used to derive the thickness of the BBL and to describe the mean turbulent properties within the BBL. Time series temperature data from thermistor chains were used to characterize the thermal structure of the lake and the basin-scale internal wave field in the lake that was shown to force the turbulent field in the BBL. A clear connection between the dynamics of the BBL and the large-scale features of the flow is presented. The time history of the thickness of the BBL, the mixing in the BBL and the resulting cross-shore flux were shown to vary with the phase of the basin-scale internal wave field. Detailed comparison of simulation results with field data revealed that the model captured well the lake hydrodynamics and the spatial and temporal evolution of energetics of the BBL. Together, field data and numerical modelling provided a clear characterization of the dynamics of the turbulent BBL and its central role in setting up a boundary layer mass flux up the slope from the lake bottom to the height of the metalimnion. Both the turbulent environment in the BBL and the mass flux are of great importance for the ecological processessing of material in a lake.

Dynamics of a large tropical lake: Lake Maracaibo

The dynamics of a large tropical lake, Lake Maracaibo, Venezuela, are described using field data and the 3D Estuary and Lake Computer Model (ELCOM). ADCP data from November 1998 and CTD data spanning September 1998 to April 1999 are presented. Seawater enters Lake Maracaibo via an augmented natural connection to the Gulf of Venezuela, which allows an influx of seawater and results in almost perenial salt stratification within the lake. Spatially varying wind forcing is found to be necessary to simulate an observed basin-scale cyclonic gyre. The gyre maintains a doming of isopycnals through a geostrophic balance that lifts high-salinity bottom water closer to the surface where it is entrained into the surface mixing layer and subsequently advected by wind-induced circulations. Horizontal excursions of saline bottom water result in considerable variability of salinity stratification at any given location in the lake. September to December (wet season) was characterized by relatively high river inflow and weak winds, resulting in weak forcing of lake circulation and weak basin-wide vertical salt flux. January to April (dry season) was characterized by relatively weak river inflow and strong winds, resulting in strong forcing of lake circulation and enhanced, basin-wide vertical salt flux. The dry season of 1999 was relatively wet (compared with other dry seasons, but still drier than the previous wet season) and there was no indication of a saline underflow occurring from Maracaibo Strait into Lake Maracaibo. The combination of strong wind forcing, low river inflow (compared with the wet season), and little or no saline intrusion during the dry season of 1999 resulted in almost complete flushing of saline bottom water.

Basin‐scale motion in stratified Upper Lake Constance

This paper describes experimental and modeled wind‐induced oscillations in Upper Lake Constance with an emphasis on a coherent understanding of the basin‐scale internal dynamics in this example of a large and stratified lake. Data were collected with eight Lake Diagnostic Systems (LDSs) consisting of thermistor chains and wind anemometers. The isotherm displacements as measured by the LDSs were interpreted using the three‐dimensional hydrodynamic Estuary and Lake Computer Model (ELCOM). Three types of basin‐scale waves were found to dominate the wave motion: the vertical mode‐one Kelvin wave that had an observed period around 90 h, two vertical mode‐one Poincaré waves that had periods near 8 h and 12 h, and a vertical mode‐two Poincaré wave that had a period near 14 h. After strong westerly winds, upwelling of cold bottom water was observed east of the Sill of Mainau, where the lake's two subbasins connect. The width and length ratios of the subbasins, spatial variations of the wind field, and rotational effects over the lake are shown to play critical roles in the details of the upwelling structure. A sudden fall of the isotherms in Lake Überlingen formed a surge. The reflection of the surge from the northwestern boundary induced a vertical mode‐two response leading to an intrusion in the metalimnion that caused a three‐layer velocity structure in the smaller subbasin.

Modeling circulation in lakes: Spatial and temporal variations

The influence of spatial and temporal variations in wind forcing on the circulation in lakes is investigated using field data and the three‐dimensional Estuary and Lake Computer Model (ELCOM) applied to Lake Kinneret. Lake Kinneret field data from six thermistor chains and eight wind anemometers deployed during July 2001 are presented. Internal wave motions are well reproduced by the numerical model when forced with a spatially uniform wind taken from a station near the lake center; however, simulated seiche amplitudes are too large (especially vertical mode 2) and lead observations by 3–10 h (for a 24‐h period wave) at different locations around the lake. Consideration of the spatial variation of the wind field improves simulated wave amplitude, and phase error at all stations is reduced to less than 1.5 h. This improvement is attributable to a better representation of the horizontally averaged wind stress and can be reproduced with a spatially uniform wind that has the same horizontally averaged wind stress as the spatially varying wind field. However, a spatially varying wind field is essential for simulating mean surface circulation, which is shown to be predominantly directly forced by the surface‐layer‐averaged wind stress moment.