While covering only 0.5% of the land area, the global fluvial network is critical for ecological processes and human life. Rivers and streams contribute to atmospheric mass and energy exchanges, support biodiversity on the Earth, and affect the global biogeochemical cycles. 
Evaporation from these dynamic water surfaces is at the core of physical, chemical, and biological processes of fluvial ecosystems. This DFG funded project aims at incorporating salient physical processes that affect flow characteristics, energy content, and surface-air interactions to constrain surface heat fluxes over water streams. We will employ state-of-the-art equipment in our laboratory and field measurements to identify dominant fluvial and environmental factors that govern evaporation dynamics to quantify evaporative mass loss rates from rivers and streams.