Water stores and flows in the Andrews Forest are controlled by, and shape, the topography, climate, and vegetation in the landscape, while also affecting human uses of streams, rivers, and water resources. The hydrology of the Andrews Forest is representative of steep forested ecosystems of much of the Pacific Northwest west of the crest of the Cascade Range, from Vancouver, Canada to Arcata, California. Distinctive features of the hydrologic setting of this region include a mild climate with wet winters and dry summers; massive, conifer, evergreen forests with high leaf area that can intercept, store, and transpire large quantities of water; thin soils on steep, highly weathered hillslopes which facilitate rapid water flux from slopes to channels; and transient snowpacks that can contribute to extreme regional floods. Water flows from the Andrews Forest influence downstream communities including the cities of Eugene, Salem, and Portland. The Andrews Forest has a long history of research using experimental watersheds, tracer and water dating studies, process and ecophysiological studies, analyses of soil hydrologic properties, and other approaches.