- There have been changes in water yield (Q) and evapotranspiration (ET) in unmanaged forests of the southern Appalachians over time. - Q increased from 1938-1970s in low elevation watersheds but decreased 22% from the 1970s-2013, while ET initially declined but increased markedly since the 1980s. - Changes in precipitation (P) and potential evapotranspiration (PET) explain some changes in Q and ET, but shifts in forest species composition and structure also contributed, potentially decreasing Q by up to 18% in some years. - The study found that both climate factors and changes in forest structure and species played a role in altering the water balance of