PNNL

Abstract

We quantify the spatio-temporal variability of Congo Basin surface water fluxes using satellite observations of the isotopic composition of water vapor. We estimate basin and sub-basin evapotranspiration minus precipitation (ET-P) between 2003 and 2018, and time-averaged evapotranspiration and net river fluxes to provide new insights into the water balance of the region. Our findings show that atmospheric water deficits (ET-P>0) are largest and occur most frequently in four quadrants of the Congo Basin between 2003-2007, but decline thereafter. By differencing our new water balance estimates with gravity-based terrestrial water storage changes and precipitation observations, we confirm that (1) ET is the largest moisture source in the Congo Basin (temporally and spatially averaged ET/P > 70%) and (2) river outflow is largest in the Western Congo, corresponding to more rivers and higher flow rates. Our results confirm the importance of ET in modulating the Congo water cycle relative to other water sources. Moreover, declining Congo atmospheric water deficits during this time are consistent with contemporaneous observed increases in Congo biomass and suggest limited sensitivity of the coupling between Congo water and carbon cycles to climate-induced water variability.