Forests play a vital role in sustaining water resources and aquatic ecosystems. Forest disturbance, both natural (e.g., wildfire, insects, disease, windstorms, drought) and human (e.g., timber harvesting, land conversion) caused, can have a profound effect on hydrologic, geomorphic and ecologic processes. With climate change, natural disturbances are becoming more frequent and catastrophic. This, together with growing human disturbance, will undoubtedly affect water resources and consequently have significant implications for land managers and policy makers. Our understanding of hydrologic and ecologic response to accelerated environmental and land use change is key to the development of adaptive and mitigating strategies ensuring the continued security of water supplies and ecological values.