Methane and carbon dioxide emissions from tropical reservoirs: Significance of downstream rivers

Guerin, Frédéric; Abril, Gwénaël; Richard, Sabine; Burban, Benoît; Reynouard, Cécile; Seyler, Patrick; Delmas, R.

doi:10.1029/2006gl027929

Cited by 220 publications

(166 citation statements)

References 14 publications

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“…During periods of water stratification, the carbon coming from organic carbon mineralization in the sediment may be trapped in the hypolimnion and may not contribute to the CO 2 flux from the water to the atmosphere (Cardoso et al, 2013). Furthermore, it is important to highlight that the contribution of carbon mineralization in the sediment to the pCO 2 at the surface can also be regulated by other factors such as CO 2 saturation in the water and the depth of the reservoir (Guérin et al, 2006). Moreover, when the river plunges and flows at the bottom of the reservoir, the water flow can disturb the sediment and enhance the carbon flux from the sediment to the hypolimnion, which can affect the contribution of organic carbon mineralized on the sediment to the amount of carbon emitted by the reservoir.…”

Section: Pco 2 Driven By Phytoplanktonmentioning

confidence: 99%

The effects of river inflow and retention time on the spatial heterogeneity of chlorophyll and water–air CO<sub>2</sub> fluxes in a tropical hydropower reservoir

et al. 2015

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Abstract. Abundant research has been devoted to understanding the complexity of the biogeochemical and physical processes that are responsible for greenhouse gas (GHG) emissions from hydropower reservoirs. These systems may have spatially complex and heterogeneous GHG emissions due to flooded biomass, river inflows, primary production and dam operation. In this study, we investigated the relationships between the water-air CO 2 fluxes and the phytoplanktonic biomass in the Funil Reservoir, which is an old, stratified tropical reservoir that exhibits intense phytoplankton blooms and a low partial pressure of CO 2 (pCO 2 ). Our results indicated that the seasonal and spatial variability of chlorophyll concentrations (Chl) and pCO 2 in the Funil Reservoir are related more to changes in the river inflow over the year than to environmental factors such as air temperature and solar radiation. Field data and hydrodynamic simulations revealed that river inflow contributes to increased heterogeneity during the dry season due to variations in the reservoir retention time and river temperature. Contradictory conclusions could be drawn if only temporal data collected near the dam were considered without spatial data to represent CO 2 fluxes throughout the reservoir. During periods of high retention, the average CO 2 fluxes were 10.3 mmol m −2 d −1 based on temporal data near the dam versus −7.2 mmol m −2 d −1 with spatial data from along the reservoir surface. In this case, the use of solely temporal data to calculate CO 2 fluxes results in the reservoir acting as a CO 2 source rather than a sink. This finding suggests that the lack of spatial data in reservoir C budget calculations can affect regional and global estimates. Our results support the idea that the Funil Reservoir is a dynamic system where the hydrodynamics represented by changes in the river inflow and retention time are potentially a more important force driving both the Chl and pCO 2 spatial variability than the in-system ecological factors.

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Section: Pco 2 Driven By Phytoplanktonmentioning

confidence: 99%

The effects of river inflow and retention time on the spatial heterogeneity of chlorophyll and water–air CO<sub>2</sub> fluxes in a tropical hydropower reservoir

et al. 2015

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“…Besides the difference in water velocity between the two places, the dissolved CO 2 in the hypolimnion at Zigui probably contributed significantly to the high CO 2 flux at Sandouping because of the disturbance by turbines. Rivers downstream of dams have been considered as contributing a significant fraction of the CO 2 emission from hydroelectric systems (Guérin et al, 2006;Kemenes et al, 2011). CO 2 emissions downstream from hydroelectric dams were often reported to be significantly larger than that upstream from hydroelectric dams (Roland et al, 2010;Wang et al, 2011).…”

Section: Environmental Factors Influencing Co 2 Fluxmentioning

confidence: 99%

Spatial and seasonal variability of CO2 flux at the air-water interface of the Three Gorges Reservoir

Yang¹,

Lu²,

Wang³

et al. 2013

Journal of Environmental Sciences

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Diffusive carbon dioxide (CO 2 ) emissions from the water surface of the Three Gorges Reservoir, currently the largest hydroelectric reservoir in the world, were measured using floating static chambers over the course of a yearlong survey. The results showed that the average annual CO 2 flux was (163.3 ± 117.4) mg CO 2 /(m 2 ·hr) at the reservoir surface, which was larger than the CO 2 flux in most boreal and temperate reservoirs but lower than that in tropical reservoirs. Significant spatial variations in CO 2 flux were observed at four measured sites, with the largest flux measured at Wushan (221.9 mg CO 2 /(m 2 ·hr)) and the smallest flux measured at Zigui (88.6 mg CO 2 /(m 2 ·hr)); these differences were probably related to the average water velocities at different sites. Seasonal variations in CO 2 flux were also observed at four sites, starting to increase in January, continuously rising until peaking in the summer (JuneAugust) and gradually decreasing thereafter. Seasonal variations in CO 2 flux could reflect seasonal dynamics in pH, water velocity, and temperature. Since the spatial and temporal variations in CO 2 flux were significant and dependent on multiple physical, chemical, and hydrological factors, it is suggested that long-term measurements should be made on a large spatial scale to assess the climatic influence of hydropower in China, as well as the rest of the world.

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“…Methane emissions from fresh waters and estuaries occur through a number of pathways including (1) continuous or episodic diffusive flux across water surfaces, (2) ebullition flux from sediments, (3) flux mediated through the aerenchyma of emergent aquatic macrophytes (plant transport) in littoral environments, and also for reservoirs, (4) degassing of CH 4 in the turbines, and (5) elevated diffusive emissions in rivers downstream of the turbines especially if water through the turbines is supplied from anoxic CH 4 -rich water layers in the reservoir (Bastviken et al, 2004;Guérin et al, 2006Guérin et al, , 2016. It is very rare that complete emission budgets include all these types of fluxes.…”

Section: Other Inland Water Systems (Lakes Ponds Rivers Estuaries)mentioning

confidence: 99%

The global methane budget 2000–2012

Saunois

Bousquet

Poulter

et al. 2016

Earth Syst. Sci. Data

944

733

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Abstract. The global methane (CH 4 ) budget is becoming an increasingly important component for managing realistic pathways to mitigate climate change. This relevance, due to a shorter atmospheric lifetime and a stronger warming potential than carbon dioxide, is challenged by the still unexplained changes of atmospheric CH 4 over the past decade. Emissions and concentrations of CH 4 are continuing to increase, making CH 4 the second most important human-induced greenhouse gas after carbon dioxide. Two major difficulties in reducing uncertainties come from the large variety of diffusive CH 4 sources that overlap geographically, and from the destruction of CH 4 by the very short-lived hydroxyl radical (OH). To address these difficulties, we have established a consortium of multi-disciplinary scientists under the umbrella of the Global Carbon Project to synthesize and stimulate research on the methane cycle, and producing regular (∼ biennial) updates of the global methane budget. This consortium includes atmospheric physicists and chemists, biogeochemists of surface and marine emissions, and socio-economists who study anthropogenic emissions. Following Kirschke et al. (2013), we propose here the first version of a living review paper that integrates results of top-down studies (exploiting atmospheric observations within an atmospheric inverse-modelling framework) and bottom-up models, inventories and data-driven approaches (including process-based models for estimating land surface emissions and atmospheric chemistry, and inventories for anthropogenic emissions, data-driven extrapolations). . Top-down inversions consistently infer lower emissions in China (∼ 58 Tg CH 4 yr −1 , range 51-72, −14 %) and higher emissions in Africa (86 Tg CH 4 yr −1 , range 73-108, +19 %) than bottom-up values used as prior estimates. Overall, uncertainties for anthropogenic emissions appear smaller than those from natural sources, and the uncertainties on source categories appear larger for top-down inversions than for bottom-up inventories and models.The most important source of uncertainty on the methane budget is attributable to emissions from wetland and other inland waters. We show that the wetland extent could contribute 30-40 % on the estimated range for wetland emissions. Other priorities for improving the methane budget include the following: (i) the development of process-based models for inland-water emissions, (ii) the intensification of methane observations at local scale (flux measurements) to constrain bottom-up land surface models, and at regional scale (surface networks and satellites) to constrain top-down inversions, (iii) improvements in the estimation of atmospheric loss by OH, and (iv) improvements of the transport models integrated in top-down inversions.

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Methane and carbon dioxide emissions from tropical reservoirs: Significance of downstream rivers

Cited by 220 publications

References 14 publications

The effects of river inflow and retention time on the spatial heterogeneity of chlorophyll and water–air CO<sub>2</sub> fluxes in a tropical hydropower reservoir

The effects of river inflow and retention time on the spatial heterogeneity of chlorophyll and water–air CO<sub>2</sub> fluxes in a tropical hydropower reservoir

Spatial and seasonal variability of CO2 flux at the air-water interface of the Three Gorges Reservoir

The global methane budget 2000–2012

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Methane and carbon dioxide emissions from tropical reservoirs: Significance of downstream rivers

Cited by 220 publications

References 14 publications

The effects of river inflow and retention time on the spatial heterogeneity of chlorophyll and water–air CO&lt;sub&gt;2&lt;/sub&gt; fluxes in a tropical hydropower reservoir

The effects of river inflow and retention time on the spatial heterogeneity of chlorophyll and water–air CO&lt;sub&gt;2&lt;/sub&gt; fluxes in a tropical hydropower reservoir

Spatial and seasonal variability of CO2 flux at the air-water interface of the Three Gorges Reservoir

The global methane budget 2000–2012

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Product

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The effects of river inflow and retention time on the spatial heterogeneity of chlorophyll and water–air CO<sub>2</sub> fluxes in a tropical hydropower reservoir

The effects of river inflow and retention time on the spatial heterogeneity of chlorophyll and water–air CO<sub>2</sub> fluxes in a tropical hydropower reservoir