Ecosystem water use through evapotranspiration is closely coupled with ecosystem productivity, water availability, and water supply. Although numerous hydrological models exist, accurately estimating water use remains challenging because of model deficiency or difficulty of model use in practice. To improve model accuracy and user experience, Forest Service researchers (including those at the agency’s Eastern Forest Environmental Threat Assessment Center) working through the U.S.-China Carbon Consortium combined water use or evapotranspiration data from global eddy covariance flux measurements at more than 200 monitoring sites, multiple year remote sensing products, and statistical modeling. Their results produced a new set of formulas that can help models better quantify landscape-level water and carbon balances with readily available meteorological and biophysical information. Scientists world-wide are applying these easy-to-use formulas to map water supply and ecosystem productivity for large basins or regions. In addition, the formulas can help users understand water stress and carbon-water tradeoffs in different ecosystems under climate change and variability and management scenarios.