Evaporation remains the component of the water and energy balances that is the hardest to quantify and measure, particularly in mountainous environments and hard to access sites. We use data from two catchments that we have instrumented, one in Burkina Faso (Tambarga, Gourma region) and one in Switzerland (Vallon de Nant, Vaud Alps) to estimate the evaporation with and with out use of stable isotopes. In both catchments, isotope data is being collected at a catchment scale from various components of the hydrologic cycle (glacier, stream, ground water, precipitation), and in Burkina Faso, at the tree scale (soil, xylem). In both catchments, we use apparent enrichment in isotopic values to infer evaporation, along the flow paths, and in Burkina Faso along the travel time within the tree. These results will be combined with hydro-meteorological measures to improve uncertainty estimates of the water fluxes in the catchments and at the tree scales.