Démarche de modélisation d'un écosystème lacustre : application au Lac de Pareloup

Salençon, Marie-José; Thébault, Jean-Marc

doi:10.1051/hydro:1994015

Cited by 7 publications

(11 citation statements)

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“…En 1995, la mise en place de la thermocline est agitée, les périodes de stratification et de mélange se succédant rapidement. Nous avons vu dans nos études précé-dentes (Salençon & Thibault 1995, 1996, 1997, l'importance de telles situations pour la distribution des nutriments et, en particulier, la disponibihté de la silice pour le peuplement printanier de diatomées. En 1993, du fait de la baisse du plan d'eau au printemps, aucune véritable stratification n'a été observée.…”

Section: La Retenue De Pareloupunclassified

Evolution saisonnière de la physico-chimie et du phytoplancton dans la retenue de Pareloup sur une longue période (1983-1998) : incidence d'une vidange totale

Thébault

2002

Ann. Limnol. - Int. J. Lim.

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La retenue de Pareloup a été étudiée depuis 1983. En 1993, elle a été entièrement vidangée ce qui a permis d'étudier l'effet de cette perturbation sur l'écosystème. Ce papier fait la synthèse de l'ensemble des données recueillies depuis le début de l'étude, et décrit l'évolution avant et après la vidange, des variables physico-chimiques et du peuplement phytoplanctonique. Un suivi de 16 ans permet de s'affranchir des années exceptionnelles et de voir à long terme comment les conditions environnementales et l'écosystème évoluent. Les concentrations de nitrates ont augmenté en 1986 dans l'ensemble du bassin versant et dans la retenue. Elles sont en légère augmentation, ou stabilisées selon les entrées, les années suivantes. L'accroissement des concentrations de silice et de nitrates observées dans la retenue après la vidange ont pour origine l'augmentation des apports liée à trois années pluvieuses et non la vidange elle-même. Le fonctionnement de l'écosystème a été fortement perturbé l'année qui a suivit la vidange : disparition des espèces dominantes du phytoplancton et développement d'espèces jusqu'alors peu abondantes. L'éco-système a ensuite retrouvé son cycle initial dès 1995. La diminution du temps de séjour semble favoriser le développement des diatomées centrales {Aulacoseira sp.) au détriment d'Astèrionella formosa. Compte tenu du rôle d'A formosa dans le piégeage du phosphore par sédimentation, la dominance d'Aulacoseira certaines années pourrait perturber l'évolution estivale de la retenue. Seasonal evolution of the physico-chemistry and the phytoplankton of Pareloup reservoir over a long period (1983-1998) : impact of total drainingKeywords : phytoplankton, physico-chemical cycles, dammed lake, draining, diatoms, Asterionellaformosa, Aulacoseira. Lake Pareloup has been studied since 1983. In 1993 it was completely drained, providing an opportunity to study the effect of this disturbance on the ecosystem. This paper gives a synthesis of all data collected since thé beginning óf4he study.and describes the physico-chemical variables and phytoplankton population before, and subsequent to, drainage. The results of monitoring over a 16 year period provide a long-term overview of environmental conditions and ecosystem development, compensating for undue disturbance in data from exceptional years. Nitrate concentrations increased slightly in 1986 in the watershed and in the lake, but stabilised in the following years. The observed post-drainage increased concentrations of silica and nitrates in the lake is attributed to increased inflow during three years of exceptional rainfall and not to the drainage itself. Ecosystem function was strongly disturbed in the year following drainage, with the replacement of the dominant phytoplanktonic species by species previously not very abundant. The ecosystem reverted to its original condition from 1995. A reduction in residence time seems to favour the development of centric diatoms (Aulacoseira sp) to the detriment of A. formosa. Considering the role of A. formosa in tr...

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Section: La Retenue De Pareloupunclassified

Evolution saisonnière de la physico-chimie et du phytoplancton dans la retenue de Pareloup sur une longue période (1983-1998) : incidence d'une vidange totale

Thébault

2002

Ann. Limnol. - Int. J. Lim.

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Section: Simulationsmentioning

confidence: 99%

“…Thus, any apparently calm water body, such as a lake, is continuously animated with complex water circulations; these movements, linked to its topography, to meteorological conditions and to the management of hydraulic installations, continually determine the thermal structure of the system. Such movements are associated with time scales from minutes to several hours, and constitute a highly variable environment for the phytoplankton (Spigel & Imberger 1987, Salençon & Thébault 1997.The vertical structure of the water column, due to surface mixing, determines the phytoplankton environment, as it influences the distribution of phytoplankton within the vertical gradients of light and temperature. The possible ecological advantage offered by the mobility of Microcystis is tackled here in terms of the amount of light energy colonies can exploit.…”

mentioning

confidence: 99%

Functional analysis of Microcystis vertical migration: a dynamic model as a prospecting tool. II. Influence of mixing, thermal stratification and colony diameter on biomass production

Rabouille

Salençon²

2005

Aquat. Microb. Ecol.

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YOYO is a deterministic model developed to represent the growth and vertical movement of Microcystis sp. colonies in the water column. Migration of colonies is represented in the model through the dynamics of carbon-reserve metabolism during photosynthesis and biosynthesis. It was used to quantify combined impacts of light, temperature and mixing on the growth and migration of colonies with different diameters. These 3 factors characterise a vertically non-homogeneous water column. Although conditions of simulation are schematic, they allow identification of situations in which the ability to regulate buoyancy gives Microcystis an advantage over non-mobile phytoplankton. Even if some vertical structures appear unfavourable for the exploitation of light energy, they nevertheless offer some advantages for the access to nutrients. Each diameter has particular benefits, and the increase in diameter observed throughout the year is probably an ecological adaptation to fluctuations in the environment at a seasonal scale.KEY WORDS: Microcystis · Photosynthesis · Carbohydrates · Vertical migration · Hydrodynamics · Mixing zone · Thermocline · 1-D mathematical model Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 39: [281][282][283][284][285][286][287][288][289][290][291][292] 2005 ( Rabouille et al. 2003). It simulates, at a daily scale, changes in growth and vertical migration of colonies due to the dynamics of the metabolism of carbon reserves during photosynthesis and biosynthesis. A previous analysis of this model under permanent conditions of light and temperature in a non-turbulent water column permitted us: (1) to independently explore the influence of light and of temperature on the migration pattern and (2) to test the variability of these migratory responses as a function of colony diameter (Rabouille et al. 2005). In the present study, we have analysed the combined influence of light, temperature and mixing on the growth and migration of colonies with different diameters. Most of the simulated diameters were chosen according to field observations in the Grangent reservoir (Loire, France) and are thus representative of colony sizes actually found in this reservoir throughout spring and summer. The largest diameters, though much less common, were nevertheless tested in the model, in order to cover the largest possible range of colony sizes and to estimate the behaviour of such colonies. Present simulations are not intended to represent realistic conditions. They are part of a model sensitivity analysis with regard to specific forcing conditions. BRIEF DESCRIPTION OF THE MODELYOYO is a deterministic model (1-dimensional vertical) intended to represent the growth and vertical movements of a population of Microcystis sp. colonies in the water column of a lake. A complete description of the model structure is given in Rabouille et al. (2005); here, we briefly outline the main components and relations. The growth model is based on a mass balance. It focuses...

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“…We simulated the hydrodynamic behaviour of the reservoir of Bimont with the model EOLE (Salençon, 1997;Salençon and Thébault, 1997). EOLE is a hydrodynamic model (one-dimensional vertical model), based on the representation of individual physical mechanisms, taking into account the bathymetry of the reservoir, surface energy exchanges, and throughflow in the reservoir (rivers, pumping, turbining, residual stream flow, etc.).…”

Section: Eole Modelmentioning

confidence: 99%

“…To account for the effect of climate change we used the latest RCP emission scenarios (van Vuuren et al, 2011) of a regionalised climate model. We used the model EOLE (Salençon, 1997;Salençon and Thébault, 1997) to simulate the hydrodynamic and thermal behaviour of the reservoir of Bimont in the medium term and in the long term . The paper demonstrates a methodology to predict the effects of climate change on reservoir hydrodynamics that may be applied to other inland water bodies.…”

Section: Introductionmentioning

confidence: 99%

Simulation of the hydrodynamic behaviour of a Mediterranean reservoir under different climate change and management scenarios

Prats¹,

Salençon²,

Gant³

et al. 2017

J Limnol

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One of the most important current issues in the management of lakes and reservoirs is the prediction of global climate change effects to determine appropriate mitigation and adaptation actions. In this paper we analyse whether management actions can limit the effects of climate change on water temperatures in a reservoir. For this, we used the model EOLE to simulate the hydrodynamic and thermal behaviour of the reservoir of Bimont (Provence region, France) in the medium term and in the long term (2066-2095) using regionalised projections by the model CNRM-CERFACS-CNRM-CM5 under the emission scenarios RCP 4.5 and RCP 8.5. Water temperature projections were compared to simulations for the reference period 1993-2013, the longest period for which we had year-long data for both hydrology and meteorology. We calibrated the model using profile measurements for the period 2010-2011 and we carried an extensive validation and assessment of model performance. In fact, we validated the model using profile measurements for 2012-2014, obtaining a root mean square error of 1.08°C and mean bias of -0.11°C, and we assured the consistency of model simulations in the long term by comparing simulated surface temperature to satellite measurements for 1999-2013. We assessed the effect of the use of synthetic input data instead of measured input data by comparing simulations made using both kinds of data for the reference period. Using synthetic data resulted in slightly lower (-0.3°C) average and maximum epilimnion temperatures, a somewhat deeper thermocline, and slightly higher evaporation (+7%). To investigate the effect of different management strategies, we considered three management scenarios: i) bottom outlet and present water level; ii) bottom outlet and elevated water level; and iii) surface outlet and elevated water level. According to the simulations, the reservoir of Bimont will have a low rate of warming of the epilimnion of 0.009-0.024°C·yr -1 , but a rapid hypolimnion warming of 0.013-0.028°C·yr -1 . The increase in surface temperatures will augment evaporation. However, the length of the stratification period and the thermocline depth are not expected to change. Elevating the water level and using a surface outlet in the reservoir of Bimont, would result in reductions of surface temperature of a similar magnitude as the expected increase because of climate change.

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Démarche de modélisation d'un écosystème lacustre : application au Lac de Pareloup

Cited by 7 publications

References 1 publication

Evolution saisonnière de la physico-chimie et du phytoplancton dans la retenue de Pareloup sur une longue période (1983-1998) : incidence d'une vidange totale

Evolution saisonnière de la physico-chimie et du phytoplancton dans la retenue de Pareloup sur une longue période (1983-1998) : incidence d'une vidange totale

Functional analysis of Microcystis vertical migration: a dynamic model as a prospecting tool. II. Influence of mixing, thermal stratification and colony diameter on biomass production

Simulation of the hydrodynamic behaviour of a Mediterranean reservoir under different climate change and management scenarios

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