Construction and Validation of Lake Biwa Basin Simulation Model with Integration of Three Components of Land, Lake Flow, and Lake Ecosystem

祐一, 佐藤; 英司, 小松; 英明, 永禮; 浩, 上原; 岳史, 湯浅; 卓也, 大久保; 高弘, 岡本; 再奎, 金

doi:10.2965/jswe.34.125

Cited by 7 publications

(3 citation statements)

References 13 publications

(1 reference statement)

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“…The use of a high-resolution flow model can be a powerful approach for simulating the massive loss of submerged macrophytes. To date, various models have been proposed for simulating lake circulation (e.g., Akitomo et al 2009), water temperature and the thermocline (e.g., Koue et al 2018), dissolved oxygen (Kitazawa et al 2010), primary production (Sato et al 2011), and other features at seasonal and interannual time scales; nevertheless, the grid resolutions of these models are insufficient for representing the detailed flow field with a focus on submerged macrophytes. In this context, previous studies have proposed a theoretical framework and bulk models for the fluid force acting on submerged macrophytes (e.g., Luhar and Nepf 2011;Hayashi and Konno 2007).…”

Section: Introductionmentioning

confidence: 99%

High-resolution flow simulation in Typhoon 21, 2018: massive loss of submerged macrophytes in Lake Biwa

Nakada

Haga

Iwaki

et al. 2021

Prog Earth Planet Sci

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The global activities of typhoons and hurricanes are gradually changing, and these storms can drastically affect lake ecosystems through the recession of submerged macrophytes that regulate the water quality in lakes. Using an echosounder, we captured the short-term, massive loss of submerged macrophytes attributed to the abnormal fluctuation of the water level induced by the approach of a catastrophic super typhoon in the southern basin of Lake Biwa, Japan. This paper investigates the physical processes responsible for the loss of vegetation using a high-resolution circulation model in Lake Biwa as a pilot study area. The circulation model was coupled with dynamical models of the fluid force and erosion acting on the vegetation. Our simulation successfully reproduced the water level fluctuation and high-speed current (torrent) generated by the typhoon gale. The simulated results demonstrated that the fluid force driven by the gale-induced torrent uprooted submerged macrophytes during the typhoon approach and that this fluid force (rather than erosion) caused the outflow of vegetation. As a result, this uprooting attributed to the fluid force induced the massive loss of submerged macrophytes in a large area of the southern basin, which might have increased primary production and reduced the stock of fish such as bluegill in the lake. Our model can estimate the reduction in the macrophyte height within the range of − 1.3 to − 0.4 m, suggesting that fluid forces greater than the time-averaged value (1.24 × 10−4 N) were available. Flow speeds of approximately 0.8 m/s might be the critical value that induces the fluid force acting on the uprooting of the submerged macrophytes. Our approach is practical for evaluating changes in lake environments attributed to the massive outflow of submerged macrophytes under various climate change scenarios.

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Section: Introductionmentioning

confidence: 99%

High-resolution flow simulation in Typhoon 21, 2018: massive loss of submerged macrophytes in Lake Biwa

Nakada

Haga

Iwaki

et al. 2021

Prog Earth Planet Sci

View full text Add to dashboard Cite

show abstract

“…The use of a high-resolution flow model can be a powerful approach for simulating the massive loss of submerged macrophytes. To date, various models have been proposed for simulating lake circulation (e.g., Akitomo et al, 2009), water temperature and the thermocline (e.g., Koue et al, 2018), dissolved oxygen (Kitazawa et al, 2010), primary production (Sato et al, 2011), and other features at the seasonal and interannual time scales; nevertheless, the grid resolutions of these models are insufficient for representing the detailed flow field with a focus on submerged macrophytes. In this context, previous studies proposed a theoretical framework and bulk models for the fluid force acting on submerged macrophytes (e.g., Luhar and Nepf, 2017;Hayashi and Konno, 2007).…”

Section: Introductionmentioning

confidence: 99%

High-Resolution Flow-Simulation in Typhoon 21, 2018: Massive Loss of Submerged Macrophytes in Lake Biwa

Nakada

Haga

Iwaki

et al. 2020

Preprint

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Global activities of typhoons and hurricanes are gradually changing, and these storms can drastically affect lake ecosystems through the recession of submerged macrophytes that regulate the water quality in lakes. Using an echosounder, we captured the short-term, massive loss of submerged macrophytes attributed to the abnormal fluctuation of the water level induced by the approach of a catastrophic super typhoon in the south basin of Lake Biwa, Japan. This paper investigates the physical processes responsible for the loss of vegetation using a high-resolution circulation model in Lake Biwa as a pilot study area. The circulation model was coupled with dynamical models of the fluid force and erosion acting on the vegetation. Our simulation successfully reproduced the water level fluctuation and high-speed current (torrent) generated by the typhoon gale. The simulated results demonstrate that the fluid force driven by the gale-induced torrent uprooted submerged macrophytes during the typhoon approach and that this fluid force (rather than erosion) caused the outflow of vegetation. As a result, this uprooting attributed to the fluid force induced the massive loss of submerged macrophytes in a large area of the south basin, which might have increased primary production and reduced the stock of fish such as bluegill in the lake. Our approach is practical for evaluating changes in lake environments attributed to the massive outflow of submerged macrophytes under various climate change scenarios. (227 words)

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“…Hence, it is necessary to construct a model that combines a hydrodynamic model with a hydrologic model. There are the models what do this (e.g., [3]), but there is no combined model that targets torrential rain.…”

Section: Introductionmentioning

confidence: 99%

Impact of Large Fresh Water Discharges into Hakata Bay Due to Torrential Rain Using Nested Two-Dimensional Convective-Dispersive Model

Fukuda¹,

Tabata²,

Honda³

et al. 2017

JWARP

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In this study, numerical simulation of a two-dimensional convective-dispersive model in Hakata Bay, Japan, is performed to analyze the impact of major river discharges due to torrential rain in Fukuoka City. Tank models are applied to calculate river discharges, which are taken into consideration as river inflow in the hydrodynamic model of Hakata Bay. A two-way nesting "edge" technique is developed and applied in the model in order to consider the influence of narrow and complex geographical features. The area around "Island City" and Imazu Bay are calculated in high resolution. The resulting model has high reproducibility since the calculated river discharges, tidal current, and salinity show good agreement with observed data. To analyze the impact of large river discharges, the calculation period is set from 11 September 2002 to 21 September 2002 since there was torrential rain on September 16 in the given year in Fukuoka City (163.5 mm/d). The results show that low-salinity water covered the whole of the inner part of Hakata Bay, and water of lower salinity than outer sea water (<34.0 psu) spread out to the bay's mouth two days after the torrential rain event. Fresh water covered the entire area of Imazu Bay and flowed out from the mouth of the Bay after the torrential rain event. The behavior of fresh water after a few days of torrential rain was remarkably different from normal discharge river flow. These results indicate that the environment in Imazu Bay can be degraded severely by torrential rain. Therefore, countermeasures to protect ecosystems in Hakata Bay must be examined immediately.

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Construction and Validation of Lake Biwa Basin Simulation Model with Integration of Three Components of Land, Lake Flow, and Lake Ecosystem

Cited by 7 publications

References 13 publications

High-resolution flow simulation in Typhoon 21, 2018: massive loss of submerged macrophytes in Lake Biwa

High-resolution flow simulation in Typhoon 21, 2018: massive loss of submerged macrophytes in Lake Biwa

High-Resolution Flow-Simulation in Typhoon 21, 2018: Massive Loss of Submerged Macrophytes in Lake Biwa

Impact of Large Fresh Water Discharges into Hakata Bay Due to Torrential Rain Using Nested Two-Dimensional Convective-Dispersive Model

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