Gross CO2 and CH4 emissions from the Nam Ngum and Nam Leuk sub-tropical reservoirs in Lao PDR

► We measured CO2 and CH4 emissions and calculated carbon budget of two Lao reservoirs. ► The Nam Leuk reservoir had GHG fluxes comparable to other tropical reservoir. ► In spite of vegetation clearance this 10 year-old reservoir was a carbon source. ► The Nam Ngum reservoir had low CH4 fluxes and negative CO2 diffusive fluxes. ► As a consequence the 40 year-old Nam Ngum Reservoir was an annual carbon sink.