Hynicka, J. and D. Caraco. 2017. Relative and Absolute Reductions in Annual Water Yield and Non-Point Source Pollutant Loads of Urban Trees. Crediting Framework Product #2 for the project Making Urban Trees Count: A Project to Demonstrate the Role of Urban Trees in Achieving Regulatory Compliance for Clean Water. Center for Watershed Protection, Ellicott City, MD. The Center for Watershed Protection led development of a water balance model to provide an improved method for quantifying the stormwater benefits of urban tree canopy. The water balance model estimates the mean annual runoff for a single tree at maturity planted over grass or impervious cover, compared to runoff from those same sites without trees. This report provides the documentation for the model.