Timber harvesting changes the condition of forest ecosystems, which are a major influence on the characteristics of headwater streams. Such characteristics include the quantity and timing of base flow and storm flow, concentrations of sediment and dissolved nutrients, water temperature, and the stability of the stream channels. This paper explores previous studies dealing with the relationship between timber harvesting and its hydrologic effects, especially long term water yield increase. The

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... tershed disturbance threshold theory is raised and investigated in detail. The development and evaluation of a spatial decision support system, the Harvest Schedule Review System (HSRS), is then described. The HSRS will aid in the minimization of hydrological impacts of forest harvesting, along with its related, negative environmental influences. It provides a spatially and temporally explicit tool for users to analyze the hydrologic impact of forest harvest schedules.