The Congo Basin hosts the second largest tropical rainforest and the largest tropical peatland in the World, acting as an engine for the global water cycle, a crucial biodiversity hotspot, and a critical global carbon sink (both above and belowground). Nowadays, it faces increasing periods of drought and temperature extremes, resulting in a widespread risk for forest growth, i.e., CO2 uptake (greenness) and its ecohydrology. This is, hence, a threat to the stability of the giant soil carbon stock, including the world's largest tropical peatland. Specifically, the ecohydrological response of the Congo Basin to climate change and human-induced land-use change remains understudied and poorly understood. Cong’eau will unite world-leading expertise for an urgently needed integrative study of the current and future hydrological cycle of the Congo Basin. The project will advance the understanding of temporal and spatial ecohydrological variability at multiple scales, which will be achieved by a unique integration of data from the first eddy covariance stations in the region, isotope and remote sensing datasets, into a suite of improved process-based models.