Ecohydrology focuses on the interactions and interrelationships between hydrological processes and the structure and function of vegetation (Breshears 2005, Rodriguez-Iturbe 2000). It builds on a long history of watershed science that quantified how changes in vegetation (e.g., through purposeful manipulation. succession, or natural disturbances) alters water and streamflow dynamics at catchment scales (Bosch and Hewlett 1982, Vose and others 2014). Recent papers have broadened the scope to include understanding soil moisture dynamics (D'Odorinco and others 2010, Emanuel and others 2010), human-dominated landscapes (Jackson and others 2009). and the sensitivity of ecosystem transitions after disturbance (Viglizzo and others 2014). In this chapter, we focus on how drought affects the interrelationships among forest structure and function, hydrologic processes. and streamflow dynamics.