Deshmukh C.,CNRS Laboratory for Aerology |
Deshmukh C.,TERI University |
Serca D.,CNRS Laboratory for Aerology |
Delon C.,CNRS Laboratory for Aerology |
And 9 more authors.
Biogeosciences | Year: 2014
In the present study, we measured independently CH4 ebullition and diffusion in the footprint of an eddy covariance system (EC) measuring CH4 emissions in the Nam Theun 2 Reservoir, a recently impounded (2008) subtropical hydroelectric reservoir located in the Lao People's Democratic Republic (PDR), Southeast Asia. The EC fluxes were very consistent with the sum of the two terms measured independently (diffusive fluxes + ebullition Combining double low line EC fluxes), indicating that the EC system picked up both diffusive fluxes and ebullition from the reservoir. We showed a diurnal bimodal pattern of CH4 emissions anti-correlated with atmospheric pressure. During daytime, a large atmospheric pressure drop triggers CH4 ebullition (up to 100 mmol mg-2 d-1), whereas at night, a more moderate peak of CH4 emissions was recorded. As a consequence, fluxes during daytime were twice as high as during nighttime. Additionally, more than 4800 discrete measurements of CH4 ebullition were performed at a weekly/fortnightly frequency, covering water depths ranging from 0.4 to 16 m and various types of flooded ecosystems. Methane ebullition varies significantly seasonally and depends mostly on water level change during the warm dry season, whereas no relationship was observed during the cold dry season. On average, ebullition was 8.5 ± 10.5 mmol mg-2 d -1 and ranged from 0 to 201.7 mmol mg-2 d-1. An artificial neural network (ANN) model could explain up to 46% of seasonal variability of ebullition by considering total static pressure (the sum of hydrostatic and atmospheric pressure), variations in the total static pressure, and bottom temperature as controlling factors. This model allowed extrapolation of CH4 ebullition on the reservoir scale and performance of gap filling over four years. Our results clearly showed a very high seasonality: 50% of the yearly CH4 ebullition occurs within four months of the warm dry season. Overall, ebullition contributed 60-80% of total emissions from the surface of the reservoir (disregarding downstream emissions), suggesting that ebullition is a major pathway in young hydroelectric reservoirs in the tropics. © Author(s) 2014.
News Article | March 2, 2017
Phonesack Group has awarded Pöyry with the owner's engineering services assignment for the Nam Theun 1 hydropower project in Laos. The Government of Laos has an ambition to become 'the battery of South East Asia' by harnessing its natural resources in order to aid economic growth and lift Laos' people out of poverty. The 650 MW Nam Theun 1 hydro power project is located at Nam Kading River, approximately 33 km upstream of its confluence with the Mekong River and 270 km from Vientiane in Central Laos. It is a major project of the Lao and Thai Power development plan and will strongly contribute to the electrical supply security of both countries. Commercial operation is scheduled to start by the end of 2022. Pöyry has been associated with the development of this project since 1995, providing technical consultancy and basic engineering services including Feasibility Study, Social and Environment Impact Assessment and more tasks. Pöyry has been supporting the Phonesack Group, the lead developer for Nam Theun 1, since 2014. In continuation of the previous assignments preparing the Feasibility Study, Basic / Detailed Design and Supervisions of the Early Works, Pöyry is now tasked with completing the Owner's Engineer Services for the Implementation as well as the Environmental and Social Mitigation Measures of the project until completion. "Delivering clean, renewable energy projects like this can aid economic growth and social progress and help alleviate poverty in developing countries. This project further strengthens Pöyry's position as one of the world's leading hydropower engineering consultancies" says Richard Pinnock, President of Pöyry's Energy Business Group. The value of the order is not disclosed. The order will be recognised within the Energy Business Group order stock in Q1 2017. Did you know? Pöyry is an international consulting and engineering company. We deliver smart solutions across power generation, transmission & distribution, forest industry, chemicals & biorefining, mining & metals, transportation and water. Pöyry's net sales in 2016 were EUR 530 million. The company's shares are quoted on Nasdaq Helsinki (POY1V). Approximately 5500 experts. 40 countries. 130 offices.