Leon Boegman

Queen's University | QueensU · Department of Civil Engineering

Parameterizations for bottom shear stress are required to predict sediment resuspension from field observations and within numerical models that do not resolve flow within the viscous sublayer. This study assessed three observation‐based bottom shear stress (τb) parameterizations, including (a) the sum of surface wave stress and mean current (quadr...

Methane emissions from lakes will increase with climate warming. However, CH4 these emissions are not presently in the surface schemes of Global Climate Models (GCMs). Because climate projections depend on future atmospheric CH4 concentrations, a positive feedback loop is not simulated. To address this issue, a one-dimensional model was developed t...

Parameterizations for bottom shear stress are required to predict sediment resuspension from field observations and within numerical models that do not resolve flow within the viscous sublayer. This study assessed three observation-based bottom shear stress (τb) parameterizations, including (1) the sum of surface wave stress and mean current (quadr...

Deep‐water hypoxia is an environmental concern in temperate lakes. Seasonal turnover events provide a mechanism for deep‐water oxygenation; however, the lake oxygen budget and mixing dynamics during turnovers are poorly understood. In the present study, the oxygen cycle in a small dimictic lake was investigated from long‐term field measurements sup...

The wind-driven nature of large lakes suggests that the accuracy of meteorological inputs is essential for hydrodynamic modelling. Moreover, coupling between the meteorological inputs and density stratification may also influence the simulated lake behavior. To investigate wind-driven large lake processes, a high-resolution coupled Delft3D-SWAN mod...

The three-dimensional MITgcm (MIT general circulation model) was applied to simulate wind-induced baroclinic oscillations in Cayuga Lake, to obtain an understanding of the internal seiche/surge dynamics and associated mixing in long narrow lakes. The MITgcm has not been rigorously validated for closed basins against field observations. Thus, qualit...

Empirical evidence demonstrates that lakes and reservoirs are warming across the globe. Consequently, there is an increased need to project future changes in lake thermal structure and resulting changes in lake biogeochemistry in order to plan for the likely impacts. Previous studies of the impacts of climate change on lakes have often relied on a...

For enhanced public safety and water resource management, a three-dimensional operational lake hydrodynamic forecasting system, COASTLINES (Canadian cOASTal and Lake forecastINg modEl System), was developed. The modeling system is built upon the three-dimensional Aquatic Ecosystem Model (AEM3D) model, with predictive simulation capabilities develop...

Breaking nonlinear internal waves (NLIWs) of depression on boundary slopes drives mixing in the coastal ocean. Of the different breaker types, fission is most commonly observed on mild slopes of continental margins. However, fission on mild slopes has rarely been investigated in the laboratory owing to limitations on flume length. In the present wo...

Empirical evidence demonstrates that lakes and reservoirs are warming across the globe. Consequently, there is an increased need to project future changes in lake thermal structure and resulting changes in lake biogeochemistry in order to plan for the likely impacts. Previous studies of the impacts of climate change on lakes have often relied on a...

Lake Simcoe has undergone eutrophication and hypoxia since the 1960s. Climate change, leading to enhanced summer thermal stratification, has been identified as a key stressor. In this study, we modeled the impacts of climate change on hydrodynamics and biogeochemistry in Lake Simcoe by applying a 1-dimensional (vertical) model forced with A2 and B1...

A three-dimensional coupled hydrodynamic-biogeochemical model was applied to simulate and investigate causes of eutrophication in two stormwater ponds in the City of Edmonton (Alberta, Canada). The ponds differ in shape, surface area, depth and trophic state. Strong spatial gradients, in water column thermal structure and water quality state variab...

Boundary layer instability beneath internal solitary waves (ISWs) of depression may be a significant source of wave-energy dissipation and drive localized mixing and resuspension in coastal regions. Wave flume experiments were undertaken to measure the dissipation of turbulent kinetic energy in the boundary layer beneath ISWs shoaling over a flat b...

During the 1970s, harmful cyanobacteria (HFCB) were common occurrences in western Lake Erie. Remediation strategies reduced total P loads and bloom frequency; however, HFCB have reoccurred since the mid-1990s under increased system stress from climate change. Given these concurrent changes in nutrient loading and climate forcing, there is a need to...

In dimictic lakes, the stable density stratification during summer and winter inhibits vertical mixing of nutrients and oxygen. This favors the development of hypolimnetic hypoxia, which degrades cool‐water fish habitat and enhances nutrient mineralization from the sediments. Fall and spring turnover events, therefore, provide a crucial biannual li...

Waste stabilization ponds (WSPs) rely on natural processes to improve water quality. WSPs require less capital or operational resources than traditional treatment and are commonly used in rural communities or for secondary disinfection. Typically, WSPs designs use empirical equations without three-dimensional (3D) circulation, thermal stratificatio...

Sediment oxygen demand (SOD) and hypolimnetic oxygen demand (HOD) drive deep-water dissolved oxygen (DO) depletion in lakes, yet these parameters can be difficult to be measure routinely. To address this issue, we present an empirical DO depletion model from time-series measurements of hypolimnetic DO and water-column temperature profiles to estima...

We simulated bottom resuspension events in Lake Erie, using a coupled three-dimensional hydrodynamic and water quality model. Key parameters in the model, including critical bottom shear stress (τcr) and resuspension rate (α) were calibrated and validated by comparing the model output to observations. These included total suspended solid (TSS) conc...

For enhanced public safety and water resource management, a three-dimensional operational lake hydrodynamic forecast system called COASTLINES (Canadian cOASTal and Lake forecastINg modEl System) was developed. The modelling system is built upon the Aquatic Ecosystem Model (AEM3D) model, with predictive simulation capabilities developed and tested f...

Climate change affects physical and biogeochemical processes in lakes. We show significant increases in surface-water temperature (~ 0.5 °C decade−1; > 0.2% year−1) and wave power (> 1% year−1; the transport of energy by waves) associated with atmospheric phenomena (Atlantic Multidecadal Oscillation and Multivariate El Niño/Southern Oscillation) in...

Oscillating turbulent bottom boundary layers (BBLs) occur in lakes and coastal oceans. At the mesoscale level, their kinematics are usually characterized by assuming either laminar or steady turbulent flow, and applying analytical solutions or semi-empirical correlations; e.g. log-law, Stokes’ second problem, inertial dissipation method (IDM), Batc...

Waste stabilization ponds (WSPs) are a common wastewater treatment approach throughout the world. Typically, WSPs are designed with the aid of empirical equations that may not incorporate complex hydrodynamics. Whereas numerical models have been presented as an alternative, they have been limited to two dimensions or lacked validation. In the prese...

Internal wave motions in lakes are initiated by the surface wind stress. The wind pushes surface water to the lee-shore, displacing the free-surface and internal stratifying layers (thermocline) along the length of the basin. When the wind stops, gravity causes the water-surface and thermocline to oscillate in the form of basin-scale standing wave...

The basin-scale hydrodynamics associated with mean-flow motions have been well characterized in Lake Erie, but little is known about the distribution of small-scale turbulence. The present study analyzed >600 temperature microstructure casts, from multiple stations collected during the spring and summer of 1997 and 2008-09, to map the characteristi...

In stratified flow, breaking of internal waves over slopes induces resuspension of bottom sediments and transport of mass. When internal waves shoal and break, flow dynamics and mass transport differ significantly according to whether the Coriolis force is included or neglected. Despite its importance, the currents generated by breaking internal Ke...

Mixing rates and biogeochemical fluxes are commonly estimated from the rate of dissipation of turbulent kinetic energy ε as measured with a single instrument and processing method. However, differences in measurements of ε between instruments/methods often vary by one order of magnitude. In an effort to identify error in computing ε, we have applie...

Lake hydrodynamics change seasonally in response to the net heat flux through the free surface. Heating during summer causes seasonal stratification to develop, where basin‐scale hydrodynamics occur under a balance between the surface wind force, which displaces the stratification, and the restoring gravitational force, which acts to bring isotherm...

Spring and fall turnover events transport nutrients and oxygen vertically in the water columnof temperate lakes, which otherwise have stable density stratification inhibitingmixing. However, lake dynamics during turnover has received little attention in theliterature. In this study, a three-dimensional model (AEM3D) was used to simulate thehydrodyna...

Computational models often are applied to simulate water quality for management of natural and constructed aquatic systems. As part of a larger study, a three-dimensional hydrodynamic and biogeochemical model was applied to three storm-water ponds in the City of Edmonton to examine relations between nutrients and eutrophication. This paper reports...

Large-amplitude internal waves induce currents and turbulence in the bottom boundary layer (BBL) and are thus a key driver of sediment movement on the continental margins. Observations of internal wave-induced sediment resuspension and transport cover significant portions of the world's oceans. Research on BBL instabilities, induced by internal wav...

Breaking of shoaling internal solitary waves (ISWs) is important for mixing and mass transport processes in oceans and lakes. For ISWs in a two-layer stratified fluid, previous studies identified four breaker types: surging, plunging, collapsing, and fission. The latest classification of these breaker types is based on the wave slope Sw and the bot...

Turbulent parameter measurements from multiple stations were investigated to understand spatial and temporal patterns of turbulent kinetic energy dissipation rate and vertical turbulent diffusivity in Lake Erie.

A dissolved oxygen sub-model is added to a 1D bulk mixed-layer thermodynamic model. Simulated volume weighted hypolimnetic oxygen concentration drops from ~5.5 (1978-2015) to ≤3.5 mg/l under forcing from climate change scenarios (2070-2100).

In stratified coastal areas in oceans and lakes, winds and tides can excite low-frequency internal waves. They may degenerate into a train of high-frequency internal waves, such as internal solitary waves (ISWs). Breaking of ISWs over a slope affects ecosystem and water quality in coastal areas by inducing long-term transport of hypoxic water, meth...

Investigation of hydrodynamic patterns within a wastewater stabilization pond to improve treatment modeling

In marginal seas and on continental shelves, interaction of tides and topography excites internal tides, which can degenerate into internal solitary waves (ISWs). Since the breaker type of ISWs is important for sediment resuspension and long-term transport of nutrients, plankton, and hypoxic water, it is needed to categorize the breaker types accur...

Lake Trout live within narrow temperature and dissolved oxygen (DO) boundaries in the hypolimnia of stratified lakes. These species are vulnerable to environmental stressors including climate warming, which will deepen the thermocline and increase the duration and strength of thermal stratification. These processes exacerbate hypolimnetic hypoxia;...

High-resolution field data, collected during April to October of 2008–2009, were analyzed to investigate the quantitative contribution of sediment resuspension to high-turbidity events in central Lake Erie. Resuspension events were distinguished within high-turbidity events according to turbidity, fluorescence and acoustic backscatter timeseries, a...

Three-dimensional (3D) hydrostatic and nonhydrostatic versions of the MITgcm were applied to simulate the dynamics of the internal wave field (basin-scale seiches, nonlinear surges and high-frequency nonlinear internal waves, NLIWs) in Cayuga Lake, NY. The simulations were performed using up to 226 million computational cells with several horizonta...

Re-eutrophication in Lake Erie has led to new programs to reduce external phosphorus loads, and it is important to understand the interrelated dynamics of external and internal phosphorus loads. In addition to developing phosphorus load response curves for algal biomass in the western basin and hypoxia in the central basin, we used a two-dimensiona...

We have implemented two bottom boundary layer mixing sub-models in a one-dimensional bulk mixed-layer thermodynamic and dissolved oxygen model to diffuse the effects of the sediment oxygen demand from the bottom boundary condition in small lakes. In the first sub-model, bottom mixing is calculated following a mixed layer approach, whereas in the se...

Vertical flux of oxygen in lakes can play an important role in regulating the severity of hypoxia. Direct measurement of oxygen flux has remained hard due to lack of sufficient data. In this research, we focus on measuring vertical oxygen flux in a small hypoxic Canadian Shield lake using Fick’s Law� = −K�dDO dz⁄, where is the vertical turbulent di...

We have implemented two bottom boundary layer mixing sub-models in a one-dimensional bulk mixed-layer thermodynamic and dissolved oxygen model to diffuse the effects of the sediment oxygen demand from the bottom boundary condition in small lakes. In the first sub-model, bottom mixing is calculated following a mixed layer approach, whereas in the se...

Well-resolved numerical simulations of turbulent open channel flows are analyzed to evaluate the accuracy of the 2nd order structure function method (SFM) in estimating the rate of dissipation of turbulent kinetic energy within boundary layers. The objective is to assess the variation in the 2/3 Kolmogorov constants due to flow anisotropy with dist...

The three-dimensional RANS model is applied to simulate sediment resuspension events in Lake Erie. Calibrated against field observations, the model results reveal the regions with active resuspension, and are analyzed to identify mechanisms leading to resuspension.

The Great Lakes Fishery Commission sponsored a 2-day workshop that sought to enhance the ability of Great Lakes agencies to understand, predict, and ideally manage fisheries production in the face of changes in natural and anthropogenic forcings (e.g., climate, invasive species, and nutrients). The workshop brought together 18 marine and freshwater...

This article presents an overview of selected physical processes and their effects on water quality in Hamilton Harbour. An understanding of circulation and mixing processes are essential to assess the fate and transport of water quality constituents in Hamilton Harbour. Water level measurements showed that in addition to harbour and lake seiches,...

Lake Trout are a rare and valuable natural resource that are threatened by multiple environmental stressors. With the added threat of climate warming, there is growing concern among resource managers that increased thermal stratification will reduce the habitat quality of deep-water Lake Trout lakes through enhanced oxygen depletion. To address thi...

Turbulent mixing in the ocean is often quantified using observations of kinetic energy dissipation (e.g., the Osborn model). However, because direct measurement of dissipation remains a challenge, it is commonly estimated from acoustic Doppler velocity data using methods such as inertial fitting or the structure function. These methods employ Kolmo...

Lake Trout are a rare and valuable natural resource that are threatened by multiple environmental stressors. With the added threat of climate warming, there is growing concern among resource managers that increased thermal stratification will reduce the habitat quality of deep-water Lake Trout lakes through enhanced oxygen depletion. To address thi...

The bottom boundary layer in lakes lies directly above the sediments and influences both hydrodynamic processes and biogeochemical fluxes. Several parameter-based models have been developed to predict the boundary layer characteristics, but the relative accuracy and applicability of these models remains under investigated, particularly for the Grea...

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...

Near-inertial (Poincaré) waves with a period Tp ∼ 17 h are the dominant wind-induced internal wave motions in central Lake Erie and consequently have a substantial influence on lake circulation, mixing and biogeochemistry. However, due to the complex three-basin bathymetry in Lake Erie, the vertical and horizontal modal structure of these waves rem...

The Bay of Quinte, Ontario, receives excessive nutrient loads and suffers from poor water quality. The 70 km long z-shaped bay traps the nutrients due to limited flushing with Lake Ontario, leading to increased nutrient residence times. Therefore, it is important to understand the three-dimensional hydrodynamic conditions within the bay, as these d...

Internal solitary waves (ISWs) of depression are common features of coastal environments and believed to resuspend sediments where they shoal. In this study, the sediment resupension process associated with ISWs propagating over a flat bed was investigated in the laboratory. The first‐ever profile measurements of the three‐dimensional instantaneous...

The hydrodynamics and contaminant transport in the nearshore region of Lake Ontario, from Port Hope to Cobourg, were simulated. The model results were comprehensively validated against observations of water level, temperature, and currents collected during April-September, 2010. The model generally agrees well with the observations. A RMS error of...

We evaluated the accuracy of the inertial dissipation method to estimate the rate of dissipation of turbulent kinetic energy within boundary layers by performing well-resolved numerical simulations of turbulent channel flows, and comparing the dissipation calculated directly from the data, with that deduced from the frequency spectra. The convectio...

A three-dimensional hydrodynamic model (ELCOM) coupled with a biological model (CAEDYM) was calibrated with field data from Lake Simcoe (2008) and used to examine the expected impact of dreissenid mussels on the distribution of phytoplankton and nutrients, mussel energetic, and the interactions with hydrodynamic conditions. In accordance with the n...

The offshore regions of large temperate lakes are characterized by strong summer temperature stratification that limits vertical mass flux, and enables near-inertial internal wave motions. Here, we investigate the contribution of near-inertial baroclinic velocity shear on enhancing the vertical transport of dissolved oxygen (DO) through the thermoc...

A spectral wave model coupled to a depth averaged hydrodynamic model was used to simulate the wave and flow conditions in the Kingston Basin of Lake Ontario during winter storm events. The simulations were verified using wave and current profiler data collected over the 2009–10 and 2011–12 winter periods. The model was forced with outputs from the...

An ; ice-formation algorithm is implemented in the three-dimensional Estuary and Lake Computer Model, to allow simulation of hydrodynamics and the thermal structure beneath the ice during winter. The one-dimensional governing equation of heat conduction among the three layers of white ice, blue ice, and snow is solved for the formation of ice cover...

We performed numerical simulations of dissolved oxygen (DO) transfer from a turbulent flow, driven by periodic boundary-layer turbulence in the intermittent regime, to underlying DO-absorbing organic sediment layers. A uniform initial distribution of oxygen is left to decay (with no re-aeration) as the turbulent transport supplies the sediment with...

[1] The examination of hypoxia in the hypolimnion of large lakes traditionally focuses on the assessment of its spatial and temporal extent and its effect on water quality. In Lake Erie, hypoxia typically occurs between July and October in the central basin; however, there is considerable interannual variability both spatially and temporally. The p...

We have tested a dissolved oxygen (DO) transport model based on large-eddy simulation (LES) of a transitional oscillatory flow observed in the bottom boundary layer of Lake Alpnach, Switzerland. The transition from a quasi-laminar to a fully turbulent state makes this flow difficult to study with a Reynolds-averaged Navier-Stokes equation (RANSE) m...

High-resolution three-dimensional numerical modeling and field observations were used to describe the nonlinear response of Cayuga Lake to surface wind forcing. The degeneration of the basin-scale internal wave field was characterized according to the composite Froude number (G(2)), Wedderburn number (W-N), and Lake number (L-N), which are measures...