@article{fdi:010066986,
  title = {{L}ow methane ({CH}4) emissions downstream of a monomictic subtropical hydroelectric reservoir ({N}am {T}heun 2, {L}ao {PDR})},
  author = {{D}eshmukh, {C}. and {G}u{\'e}rin, {F}r{\'e}d{\'e}ric and {L}abat, {D}. and {P}ighini, {S}. and {V}ongkhamsao, {A}. and {G}uedant, {P}. and {R}ode, {W}. and {G}odon, {A}. and {C}hanudet, {V}. and {D}escloux, {S}. and {S}erca, {D}.},
  editor = {},
  language = {{ENG}},
  abstract = {{M}ethane ({CH}4) emissions from hydroelectric reservoirs could represent a significant fraction of global {CH}4 emissions from inland waters and wetlands. {A}lthough {CH}4 emissions downstream of hydroelectric reservoirs are known to be potentially significant, these emissions are poorly documented in recent studies. {W}e report the first quantification of emissions downstream of a subtropical monomictic reservoir. {T}he {N}am {T}heun 2 {R}eservoir ({NT}2{R}), located in the {L}ao {P}eople's {D}emocratic {R}epublic, was flooded in 2008 and commissioned in {A}pril 2010. {T}his reservoir is a trans-basin diversion reservoir which releases water into two downstream streams: the {N}am {T}heun {R}iver below the dam and an artificial channel downstream of the powerhouse and a regulating pond that diverts the water from the {N}am {T}heun watershed to the {X}e {B}angfai watershed. {W}e quantified downstream emissions during the first 4 years after impoundment (2009-2012) on the basis of a high temporal (weekly to fort nightly) and spatial (23 stations) resolution of the monitoring of {CH}4 concentration. {B}efore the commissioning of {NT}2{R}, 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. {A}fter the commissioning, downstream emissions were dominated by degassing which occurred mostly below the powerhouse. {O}verall, downstream emissions decreased from 10 {G}g{CH}(4) yr(-1) after the commissioning to 2 {G}g{CH}(4) yr(-1) 4 years after impoundment. {T}he downstream emissions contributed only 10 to 30% of total {CH}4 emissions from the reservoir during the study. {M}ost 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 mu mol {L}-1) and downstream emissions are negligible for the rest of the year. {E}missions downstream of {NT}2{R} 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. {T}he 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 %.},
  keywords = {{LAOS}},
  booktitle = {},
  journal = {{B}iogeosciences},
  volume = {13},
  numero = {6},
  pages = {1919--1932},
  ISSN = {1726-4170},
  year = {2016},
  DOI = {10.5194/bg-13-1919-2016},
  URL = {https://www.documentation.ird.fr/hor/fdi:010066986},
}