Hydrodynamics and mixing mechanisms in a subtropical reservoir

Ishikawa, Mayra; Bleninger, Tobias; Lorke, Andreas

doi:10.1080/20442041.2021.1932391

Cited by 16 publications

(26 citation statements)

References 69 publications

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“…We observed a strong diurnal variation in the dissipation rate (primarily during the first deployment; see Figures S5 and S8, Supplementary Material). However, in contrast to similar observations [17,63], we observed high acoustic backscatter during the night (see Figure S5b, Supplementary Material) and an increase in dissipation rates and vertical velocity occurred during the day (Figure S5b, Supplementary Material). It is important to note that high dissipation rates were present in the entire water column and not just close to the bottom where elevated acoustic backscatter was observed.…”

Section: Overall Energy Budgetcontrasting

confidence: 99%

“…We observed high acoustic backscatter in the upper part of the water column during the night and at larger depth during daytime, suggesting diurnal vertical migration of zooplankton [65]. Recent studies found higher dissipation rates at depths of high acoustic backscatter [17,63], suggesting a contribution of migrating organisms to energy dissipation. In contrast to these observations, we observed enhanced dissipation rates at depths and at times of low acoustic backscatter.…”

Section: Energy Dissipation Ratessupporting

confidence: 46%

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Energy Flux Paths in Lakes and Reservoirs

Guseva

Casper

Sachs

et al. 2021

Water

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Mechanical energy in lakes is present in various types of water motion, including turbulent flows, surface and internal waves. The major source of kinetic energy is wind forcing at the water surface. Although a small portion of the vertical wind energy flux in the atmosphere is transferred to water, it is crucial for physical, biogeochemical and ecological processes in lentic ecosystems. To examine energy fluxes and energy content in surface and internal waves, we analyze extensive datasets of air- and water-side measurements collected at two small water bodies (<10 km2). For the first time we use directly measured atmospheric momentum fluxes. The estimated energy fluxes and content agree well with results reported for larger lakes, suggesting that the energetics governing water motions in enclosed basins is similar, independent of basin size. The largest fraction of wind energy flux is transferred to surface waves and increases strongly nonlinearly for wind speeds exceeding 3 m s−1. The energy content is largest in basin-scale and high-frequency internal waves but shows seasonal variability and varies among aquatic systems. At one of the study sites, energy dissipation rates varied diurnally, suggesting biogenic turbulence, which appears to be a widespread phenomenon in lakes and reservoirs.

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Section: Overall Energy Budgetcontrasting

confidence: 99%

Section: Energy Dissipation Ratessupporting

confidence: 46%

Energy Flux Paths in Lakes and Reservoirs

Guseva

Casper

Sachs

et al. 2021

Water

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“…Comprehension of lake and reservoir hydrodynamics is key for good water quality, for drinking water safety, as well as for predicting future changes [23]. Understanding the relationships between temperature and vertical transport is key to modeling emergent ecosystem functions in a warmer world [18].…”

Section: The Assessment Of Vertical Nutrient Fluxes Also Helps Understanding Some Ecological Variationsmentioning

confidence: 99%

“…In VB, vertical mixing and nutrient fluxes increases are evident when the level decreases below 8 m and can increase several-fold when the level falls down below 12 m. Altogether, the multiple consequences of WLFs in windy tropical lakes such as VB can alter both the ecology of the reservoir lake and its suitability for sustained water exploitation by the main users. The effects we identified here should be accounted for by water managers [18,23], who should outweigh them against the particular needs of water distribution and other reservoir lake uses when making decisions that may affect the water level of reservoirs and lakes.…”

Section: The Assessment Of Vertical Nutrient Fluxes Also Helps Understanding Some Ecological Variationsmentioning

confidence: 99%

“…Such a long-term series reveals the variation in the intensity of water mixing and nutrient entrainment as a function of water level fluctuations (WLFs). Comprehension of reservoir hydrodynamics is essential for maintaining good water quality and drinking water safety, as well as for predicting future changes [23]. Furthermore, the important ecological effects and implications of vertical mixing variations are discussed so that they can be used, along with other relevant considerations, in the context of the management of tropical lakes and reservoirs [18].…”

Section: Introductionmentioning

confidence: 99%

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Vertical Boundary Mixing Events during Stratification Govern Heat and Nutrient Dynamics in Windy Tropical Lakes with High Water-Level Fluctuations: A Long-Term (2001-2018) Study

Merino–Ibarra¹,

Ramírez-Zierold²,

Valdespino-Castillo³

et al. 2021

Preprint

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Physical processes play important roles in controlling eutrophication and oligotrophication. In stratified lakes, internal waves can cause vertical transport of heat and nutrients without breaking the stratification, through boundary mixing events. Such is the case in tropical Valle de Bravo (VB) lake, where strong diurnal winds drive internal waves, boundary mixing and hypolimnetic warming during stratification periods. We monitored VB during 18 years (2001-2018) when important water-level fluctuations (WLF) occurred, affecting mixing and nutrient flux. Mean hypolimnetic temperature increase (0.06–1.04°C month-1) occurred in all the stratifications monitored. We analyzed temperature distributions and modeled the hypolimnion heat budget to assess vertical mixing between layers (26,618–140,526 m-3h-1), vertical diffusivity coefficient KZ (6.2x10-7–3.3x10-6 m2s-1) and vertical nutrient entrainment to epilimnion on monthly scale. Stability also varied as a function of WLF. Nutrient flux to the epilimnion ranged 0.36–5.99 mg m-2d-1 for soluble reactive phosphorus (SRP) and 5.8–97.1 mg m-2d-1 for dissolved inorganic nitrogen (DIN). During low water-level years, vertical nutrient fluxes increase and can account for up to &gt;40% of the total external nutrients load to the lake. Vertical mixing changes related to WLF affect nutrient recycling, their flux to sediments, ecosystemic metabolic balance and planktonic composition of VB.

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Does polymixis complicate prediction of high‐frequency dissolved oxygen in lakes and reservoirs?

Robbins,

Sadler,

Trolle

et al. 2024

Limnology & Oceanography

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As lake and reservoir ecosystems transition across major environmental regimes (e.g., mixing regime) resulting from anthropogenic change, setting predictive expectations is imperative. We tested the hypothesis that (dissolved) oxygen is more predictable in monomictic reservoirs that thermally stratify throughout the summer (warm) season compared to polymictic reservoirs that stratify intermittently. Using two‐hourly vertical profiles of oxygen, we compared daily‐aggregated errors of oxygen predictions from random forests across and within two monomictic and two polymictic reservoirs in the south‐central (subtropical) USA. Although one monomictic reservoir was typically more predictable than the polymictic reservoirs, the hypereutrophic, small monomictic reservoir had less predictable oxygen patterns potentially related to rapid oxygen cycling and intrusions of oxygenated waters in the hypolimnion without mixing. Daily mixing did not relate strongly to model errors. Water temperature, depth, and wind were the most important predictors, but were not clearly related to season or mixing. Lastly, we compared multiple model types (regression, neural network, and process‐based) in one polymictic reservoir to test how our interpretations of oxygen predictability were sensitive to model type, finding that the models generally agreed; however, the process‐based model poorly predicted oxygen in the middle of the vertical profiles (5 m) where most models performed poorly due to a temporally unstable, vacillating metalimnion. Our results suggest predicting reservoir oxygen dynamics may be easier in stratified reservoirs, but eutrophication and complex hydrodynamics may cause forecasting surprises especially for those who use or manage water resources in mono‐ or dimictic reservoirs.

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Hydrodynamics and mixing mechanisms in a subtropical reservoir

Cited by 16 publications

References 69 publications

Energy Flux Paths in Lakes and Reservoirs

Energy Flux Paths in Lakes and Reservoirs

Vertical Boundary Mixing Events during Stratification Govern Heat and Nutrient Dynamics in Windy Tropical Lakes with High Water-Level Fluctuations: A Long-Term (2001-2018) Study

Does polymixis complicate prediction of high‐frequency dissolved oxygen in lakes and reservoirs?

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