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Globally, forests cover 31% of the Earth’s land mass and are critical areas for water supply. In Australia, forested catchments provide 77% of urban water supplies to capital cities. However, recent studies have reported worldwide examples of forest damage resulting from drought or heat related events. The jarrah (Eucalyptus marginata) forests of south-west Western Australia (SWWA) have experienced both sudden and unprecedented forest collapse and profound reductions in streamflows. Projected further declines with climate change, reinforce the need to understand the hydrologic impact of forest disturbance and what management responses are needed to enhance forest resilience and productive capacity. The aim of this thesis was to understand the impact of disturbance and climate on the hydrology of the forests of SWWA, with objectives to: 1. Examine the characteristics of forest hydrology; 2. Evaluate the hydrologic response to forest disturbance and climate variability; and 3. Evaluate forest water management options in the context of forest disturbance and climate change. This thesis thus develops an understanding of the impact of disturbance and climate on the hydrology of the forests of SWWA. Using hillslope and paired catchment studies (Chapter 3), it develops an understanding of the process of infiltration and soil water dynamics and examines the hydrologic impact of forest disturbance. The studies demonstrate the important roles of infiltration, soil water dynamics, and groundwater on the forest water balance, and identify the major factors that impact forest disturbance and forest hydrology. These studies have improved understanding of factors contributing to catchment water balance, and streamflow generation processes. Four catchments underwent land use change and the impact on catchment hydrology was studied by comparing with a control catchment (Chapter 4). These paired catchment studies evaluated the impact of converting forest to agriculture and of timber