Robotic mapping of mixing and dispersion of augmented surface water in a drought frequent reservoir

Rogowski, Peter; Merrifield, Sophia; Ding, Li; Terrill, Eric; Gesiriech, Gannon

doi:10.1002/lom3.10326

Cited by 3 publications

(11 citation statements)

References 41 publications

(52 reference statements)

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“…This delay is modulated by τ ini (Sect. 4.2) and consistent with previous studies where the onset of TS was observed at night (Monismith et al, 1990;James et al, 1994;Fer et al, 2002b;Pálmarsson and Schladow, 2008) or in the morning (Rogowski et al, 2019;Sturman et al, 1999). t is a good estimate for the onset time when the water column is initially mixed ( mix = 0).…”

Section: Effects Of the Forcing Conditions On The Flushing Periodsupporting

confidence: 91%

“…The increase of discharge with depth was reported in Lake Geneva by Fer et al (2002b). Values of TS thickness and discharge can be one order of magnitude larger in deeper lakes than Rotsee (Thorpe et al, 1999;Fer et al, 2002a;Rogowski et al, 2019).…”

Section: Practical Recommendations To Predict and Measure Thermal Siphons In Other Lakesmentioning

confidence: 83%

“…We also suggest that a similar trend should be common in other temperate lakes. Most of the TS events reported for other systems were observed in late summer or autumn, corresponding to the occurrence period in Rotsee (Monismith et al, 1990;James and Barko, 1991a, b;James et al, 1994;Rogowski et al, 2019). James and Barko (1991b) showed that differential cooling in Eau Galle Reservoir (WI, USA) already developed in early summer, but during cold front events only.…”

Section: Effects Of the Forcing Conditions On The Occurrence Of Thermal Siphonsmentioning

confidence: 89%

“…( 9)). Past observations of TS reported horizontal velocities ranging from ~0.1 cm s -1 (James and Barko, 1991a, b) to ~10 cm s -1 (Roget et al, 1993;Fer et al, 2002b), with x ∼ 1 cm s -1 in most cases (Monismith et al, 1990 Sturman et al, 1999;Pálmarsson and Schladow, 2008;Rogowski et al, 2019). The cross-shore transport x and flushing timescale F are strongly dependent on the size and depth of the littoral region considered (Eqs.…”

Section: Practical Recommendations To Predict and Measure Thermal Siphons In Other Lakesmentioning

confidence: 93%

“…The cross-shore circulation was characterized by inertia, with a delay of several hours between the shift in forcing conditions and the flow reversal. Other studies have reported the presence of TS along the thalweg of narrow reservoir embayments (James and Barko, 1991a, b;James et al, 1994;Rogowski et al, 2019), but also on the sloping sides of lakes (Sturman et al, 1999;Thorpe et al, 1999;Fer et al, 2002a, b;Pálmarsson and Schladow, 2008) and between different basins (Roget et al, 1993). In most of these examples, the characteristics of TS were similar to the description of Monismith et al (1990), with a thermal stratification above the sloping bottom, inertial effects and a cross-shore velocity on the order of 1 cm s -1 .…”

Section: Introductionmentioning

confidence: 92%

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Seasonality of density currents induced by differential cooling

Doda

Ramón

Ulloa³

et al. 2021

Preprint

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Abstract. When lakes experience surface cooling, the shallow littoral region cools faster than the deep pelagic waters. The lateral density gradient resulting from this differential cooling can trigger a cold downslope density current that intrudes at the base of the mixed layer during stratified conditions. This process is known as thermal siphon (TS). TS flushes the littoral region and increases water exchange between nearshore and pelagic zones, with possible implications on the lake ecosystem. Past observations of TS in lakes are limited to specific cooling events. Here, we focus on the seasonality of the TS-induced lateral transport and investigate how the seasonally varying forcing conditions control the occurrence and intensity of TS. We base our analysis on one year of observations of TS in Rotsee (Switzerland), a small wind-sheltered temperate lake composed of an elongated shallow region. We demonstrate that TS occurs for more than 50 % of the days from late summer to winter and efficiently flushes the littoral region in ~10 hours. We further quantify the seasonal evolution of the occurrence, intensity and timing of TS. The conditions for the formation of TS are optimal in autumn, when the duration of the cooling phase is longer than the initiation timescale of TS. The decrease in surface cooling by one order of magnitude from summer to winter reduces the lateral transport by a factor of two. We interpret this transport seasonality with scaling relationships relating the daily averaged cross-shore velocity, unit-width discharge and flushing timescale to the surface buoyancy flux, mixed layer depth and lake bathymetry. The timing and duration of the diurnal flushing by TS are associated with the duration of the daily heating and cooling phases. The longer cooling phase in autumn increases the flushing duration and delays the time of maximal flushing, compared to the summer period. Our findings based on scaling arguments can be extended to other aquatic systems to assess, at a global scale, the relevance of TS in lakes and reservoirs.

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Section: Effects Of the Forcing Conditions On The Flushing Periodsupporting

confidence: 91%

Section: Practical Recommendations To Predict and Measure Thermal Siphons In Other Lakesmentioning

confidence: 83%

Section: Effects Of the Forcing Conditions On The Occurrence Of Thermal Siphonsmentioning

confidence: 89%

Section: Practical Recommendations To Predict and Measure Thermal Siphons In Other Lakesmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 92%

See 3 more Smart Citations

Seasonality of density currents induced by differential cooling

Doda

Ramón

Ulloa³

et al. 2021

Preprint

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Evolución del trazador en los flujos naturales descrita por la función de estado ф(U, E, t): análisis de las funciones asociadas y su aplicación a casos prácticos

Contaín¹,

Peña-Guzmán

2022

Tecnol. cienc. agua

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Seasonality of density currents induced by differential cooling

Doda

Ramón

Ulloa

et al. 2022

Hydrol. Earth Syst. Sci.

View full text Add to dashboard Cite

Abstract. When lakes experience surface cooling, the shallow littoral region cools faster than the deep pelagic waters. The lateral density gradient resulting from this differential cooling can trigger a cold downslope density current that intrudes at the base of the mixed layer during stratified conditions. This process is known as a thermal siphon (TS). TSs flush the littoral region and increase water exchange between nearshore and pelagic zones; thus, they may potentially impact the lake ecosystem. Past observations of TSs in lakes are limited to specific cooling events. Here, we focus on the seasonality of TS-induced lateral transport and investigate how seasonally varying forcing conditions control the occurrence and intensity of TSs. This research interprets 1-year-long TS observations from Rotsee (Switzerland), a small wind-sheltered temperate lake with an elongated shallow region. We demonstrate that TSs occur for more than 50 % of the days from late summer to winter and efficiently flush the littoral region within ∼10 h. We further quantify the occurrence, intensity, and timing of TSs over seasonal timescales. The conditions for TS formation become optimal in autumn when the duration of the cooling phase is longer than the time necessary to initiate a TS. The decrease in surface cooling by 1 order of magnitude from summer to winter reduces the lateral transport by a factor of 2. We interpret this transport seasonality with scaling relationships relating the daily averaged cross-shore velocity, unit-width discharge, and flushing timescale to the surface buoyancy flux, mixed-layer depth, and lake bathymetry. The timing and duration of diurnal flushing by TSs relate to daily heating and cooling phases. The longer cooling phase in autumn increases the flushing duration and delays the time of maximal flushing relative to the summer diurnal cycle. Given their scalability, the results reported here can be used to assess the relevance of TSs in other lakes and reservoirs.

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Robotic mapping of mixing and dispersion of augmented surface water in a drought frequent reservoir

Cited by 3 publications

References 41 publications

Seasonality of density currents induced by differential cooling

Seasonality of density currents induced by differential cooling

Evolución del trazador en los flujos naturales descrita por la función de estado ф(U, E, t): análisis de las funciones asociadas y su aplicación a casos prácticos

Seasonality of density currents induced by differential cooling

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