The global network of rivers and streams spans over 80 million kilometers and is the key to human settlement, supporting diverse aquatic ecosystems, and transporting sediment and carbon into the oceans. Evaporative losses from these important aquatic arteries affect not only water availability, but may influence chemical and biological processes of river ecosystems through changes in energy budget and water temperature. Despite progresses in quantifying evaporation from other inland water bodies (e.g., lakes, reservoirs), estimates of evaporation from rivers remain largely local and empirical lacking predictability to varying fluvial and climatic conditions at different scales. Specifically, effects of turbulence and mixing of these dynamic evaporating surfaces, aerodynamic interactions with overlying air, variable radiative regimes and flow characteristics have not been systematically incorporated into evaporation models across a hierarchy of scales. 

This project seeks to develop a physically-based framework for constraining river and stream evaporation considering a scale-appropriate energy partitioning scheme. The model will consider salient features of mixing and turbulence while accounting for variations in radiative energy inputs and flow characteristics. We will harness systematic laboratory and field measurements to identify dominant flow characteristics and environmental factors that guide upscaling of the theoretical approach to quantify evaporative losses from the fluvial network on a global scale.