Greenhouse gas emissions from flooded drylands (Kati Thanda Lake Eyre basin, Australia)

Covering 40–50% of the Earth’s surface drylands make an important contribution to the terrestrial carbon sink and the global carbon cycle. However, in addition to extended dry periods, drylands also experience extreme flood events. We will present carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) emissions from Kati-Thanda-Lake-Eyre basin in central Australia during flooding in 2019. The low basin slope resulted in a large wet of inundation (up to 33,547 km²), that remained wet for an extended period (89 to 325 days). Up-scaling the daily measured fluxes for the changing wet surface area, for the period it was wet, has the potential to result in around 115 Tg of CO₂ and 21 Gg of CH₄  emitted, and 2 Gg of N₂O consumed (Total= 117 Tg CO₂e). The low gradient and associated low volume of water transported and large wet area also resulted in the vertical flux of carbon being up to about 800 times the river transported carbon. This first-order estimate of GHG emissions from the Kati-Thanda-Lake-Eyre basin suggests that when flooded, dryland systems globally have the potential to make a significant but currently unaccounted for, contribution to global GHG emissions.