Carbon, nitrogen, phosphorus, and sediment sources and retention in a small eutrophic tropical reservoir

Némery, Julien; Gratiot, Nicolas; Doan, Phuong; Duvert, Clément; Alvarado-Villanueva, Reyna; Duwig, Céline

doi:10.1007/s00027-015-0416-5

Cited by 39 publications

(19 citation statements)

References 65 publications

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“…The same inflow-outflow mass balance method has been used to quantify N elimination in reservoirs. That is, the difference between the TN river load to a reservoir and the TN outflow through the dam is attributed to TN elimination by burial and denitrification in the reservoir (Némery et al, 2016;Tomaszek & Koszelnik, 2003). In some cases, the inflow-outflow mass balance calculations are combined with measurements of denitrification rates (David et al, 2006;Garnier et al, 1999;Koszelnik et al, 2007) and N sedimentation rates (Vanni et al, 2011).…”

Section: 1029/2019gb006222mentioning

confidence: 99%

Effects of Damming on River Nitrogen Fluxes: A Global Analysis

Akbarzadeh

Maavara

Slowinski

et al. 2019

Global Biogeochemical Cycles

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Damming creates biogeochemical hotspots along rivers that modify the riverine flow of nutrients, including nitrogen (N). Here, we quantify the impact of dams on global riverine N fluxes using a reservoir N mass balance model. In-reservoir processes represented in the model include primary production, mineralization of organic N, denitrification, and sedimentary burial. In addition, we explicitly account for N fixation as a source of N, assuming that the N to phosphorus (P) ratio of the inflow regulates the magnitude of N fixation in reservoirs. The model is scaled up via a Monte Carlo analysis that yields global relationships between N elimination in reservoirs, either by denitrification or burial, and the hydraulic residence time. These relationships are then combined with N loads to the world's dam reservoirs generated by the Global-NEWS model and the estimated N fixation fluxes. According to the results, in year 2000, worldwide N fixation in reservoirs was on the order of 70 Gmol yr −1 , while denitrification and burial in reservoirs eliminated around 270 Gmol yr −1 , equal to 7% of N loading to the global river network. The latter is predicted to double to 14% by 2030, mainly as a result of the current boom in dam building. The results further imply that, largely due to N fixation in reservoirs, damming causes a global upward shift in riverine N:P ratios, thus lessening N limitation in receiving water bodies.

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Section: 1029/2019gb006222mentioning

confidence: 99%

Effects of Damming on River Nitrogen Fluxes: A Global Analysis

Akbarzadeh

Maavara

Slowinski

et al. 2019

Global Biogeochemical Cycles

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“…When the values of N ret and R N were positive, a retention effect of nitrogen in the reservoir was shown; otherwise, the negative values showed a release effect. Nitrogen retention performance is determined by a number of factors, including hydrological and hydrodynamic conditions (inflow runoff, hydraulic residence time (HRT), velocity, and water level), nitrogen load, and water temperature in some studies, mostly using continuous monitoring data [9,28,29]. However, it is not feasible to conduct the analysis of the nitrogen retention effect and influential factors at multiple time scales due to the lack of long-term data in the area, while the coupled use of the upland watershed hydrological model (SWAT) and downstream waterbodies model (CE-QUAL-W2) was able to overcome the disadvantages mentioned above.…”

Section: Nitrogen Retention Calculation and Influential Factor Analysismentioning

confidence: 99%

Nitrogen Retention Effects under Reservoir Regulation at Multiple Time Scales in a Subtropical River Basin

Liu

Chen

et al. 2019

Water

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Reservoirs are an important nitrogen sink as a result of their retention effect, but their retention performance may vary with hydrologic conditions with time-varying characteristics, which also change them from being a sink to source over time. This study uses a coupled modelling system (Soil and Water Assessment Tool (SWAT) and a two-dimensional hydrodynamic and water quality model (CE-QUAL-W2) to analyze the nitrogen retention effect and influential factors at annual, monthly, and daily scales in Shanmei Reservoir in southeast China. The results showed that there was a positive retention effect of total nitrogen (TN), nitrate-nitrogen (NO3-N) and ammonia nitrogen (NH4-N) in most years, with average retention rates up to 12.7%, 7.83% and 26.17%, respectively. The reservoir serves mainly as a nitrogen sink at an annual scale. The monthly retention performances of TN and NO3-N were observed during the wet season (April–October) with higher water temperature and lower velocity, while a release effect occurred during the dry season (November–March). For NH4-N, which is prone to nitrification, the retention effect lasted longer, from May to December. The daily nitrogen retention process changed more dramatically, with the retention rate varying from −292.49 to 58.17%. During the period of dispatch, the regulated discharge was the primary factor of daily retention performance, while the hydraulic residence time, velocity and water level were all significantly correlated with nitrogen retention during the period without dispatch.

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“…As a consequence, bottom concentrations decrease from 500 to less than 5 µmol L −1 during these events, and the amount of CH 4 transferred from the reservoir to the downstream reaches decreases by 2 orders of magnitude and stays low during 8 to 9 months, before the CH 4 concentration in the reservoir increases again. Monomictic reservoirs like Nam Theun 2, Nam Leuk, Nam Ngum in Lao PDR (Chanudet et al, 2011), the Three Gorges Dam in China and the Cointzio Reservoir in Mexico (Némery et al, 2015) are common in the subtropics and especially in Asia, where 60 % of the worldwide hydroelectric reservoirs are. Although CH 4 emissions below amictic reservoirs like Petit Saut and Balbina are high and very significant in the total emissions (Abril et al, 2005;Kemenes et al, 2007), low emission downstream of monomictic/dimictic/polymictic reservoirs is likely to be a general feature.…”

Section: Spatial and Temporal Variations Of Downstream Emissionsmentioning

confidence: 99%

Low methane (CH<sub>4</sub>) emissions downstream of a monomictic subtropical hydroelectric reservoir (Nam Theun 2, Lao PDR)

Deshmukh

Guerin²,

Labat

et al. 2016

Biogeosciences

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Abstract. Methane (CH 4 ) emissions from hydroelectric reservoirs could represent a significant fraction of global CH 4 emissions from inland waters and wetlands. Although CH 4 emissions downstream of hydroelectric reservoirs are known to be potentially significant, these emissions are poorly documented in recent studies. We report the first quantification of emissions downstream of a subtropical monomictic reservoir. The Nam Theun 2 Reservoir (NT2R), located in the Lao People's Democratic Republic, was flooded in 2008 and commissioned in April 2010. This reservoir is a trans-basin diversion reservoir which releases water into two downstream streams: the Nam Theun River below the dam and an artificial channel downstream of the powerhouse and a regulating pond that diverts the water from the Nam Theun watershed to the Xe Bangfai watershed. We quantified downstream emissions during the first 4 years after impoundment (2009)(2010)(2011)(2012) on the basis of a high temporal (weekly to fortnightly) and spatial (23 stations) resolution of the monitoring of CH 4 concentration.Before the commissioning of NT2R, downstream emissions were dominated by a very significant degassing at the dam site resulting from the occasional spillway discharge for controlling the water level in the reservoir. After the commissioning, downstream emissions were dominated by degassing which occurred mostly below the powerhouse. Overall, downstream emissions decreased from 10 GgCH 4 yr −1 after the commissioning to 2 GgCH 4 yr −1 4 years after impoundment. The downstream emissions contributed only 10 to 30 % of total CH 4 emissions from the reservoir during the study.Most of the downstream emissions (80 %) occurred within 2-4 months during the transition between the warm dry season (WD) and the warm wet season (WW) when the CH 4 concentration in hypolimnic water is maximum (up to 1000 µmol L −1 ) and downstream emissions are negligible for Published by Copernicus Publications on behalf of the European Geosciences Union. C. Deshmukh et al.: Low methane (CH 4 ) emissions downstreamthe rest of the year. Emissions downstream of NT2R are also lower than expected because of the design of the water intake. A significant fraction of the CH 4 that should have been transferred and emitted downstream of the powerhouse is emitted at the reservoir surface because of the artificial turbulence generated around the water intake. The positive counterpart of this artificial mixing is that it allows O 2 diffusion down to the bottom of the water column, enhancing aerobic methane oxidation, and it subsequently lowered downstream emissions by at least 40 %.

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Carbon, nitrogen, phosphorus, and sediment sources and retention in a small eutrophic tropical reservoir

Cited by 39 publications

References 65 publications

Effects of Damming on River Nitrogen Fluxes: A Global Analysis

Effects of Damming on River Nitrogen Fluxes: A Global Analysis

Nitrogen Retention Effects under Reservoir Regulation at Multiple Time Scales in a Subtropical River Basin

Low methane (CH<sub>4</sub>) emissions downstream of a monomictic subtropical hydroelectric reservoir (Nam Theun 2, Lao PDR)

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Carbon, nitrogen, phosphorus, and sediment sources and retention in a small eutrophic tropical reservoir

Cited by 39 publications

References 65 publications

Effects of Damming on River Nitrogen Fluxes: A Global Analysis

Effects of Damming on River Nitrogen Fluxes: A Global Analysis

Nitrogen Retention Effects under Reservoir Regulation at Multiple Time Scales in a Subtropical River Basin

Low methane (CH&lt;sub&gt;4&lt;/sub&gt;) emissions downstream of a monomictic subtropical hydroelectric reservoir (Nam Theun 2, Lao PDR)

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Low methane (CH<sub>4</sub>) emissions downstream of a monomictic subtropical hydroelectric reservoir (Nam Theun 2, Lao PDR)