This chapter explores how forest disturbance impacts the water cycle. We present an introduction to the scope of forest disturbances in the past, present, and future; a primer on how forest disturbances affect hydrology; approaches for obtaining values of hydrologic variables; tools for ecohydrologic assessment including experiments, statistical or process modeling, satellite remote sensing, and recommendations for forest disturbance assessment and planning. This chapter focuses on forest disturbance (i.e. reductions) and does not consider afforestation.