This paper uses observed daily streamflow data to examine the flow regimealteration and how these changes might potentially affect freshwater ecosystems. Theearth surface temperature has been observed gradually increase and associate withprecipitation and atmospheric moisture changes over space and time. Climateinduced flow regime changes are examined by Indicators of Hydrologic Alterationapproach. The annual extreme water conditions (1-, 3-, 7-, 30-, 90- day annualminima or maxima) reveal larger alteration from analyzing twenty-three gaugingstations throughout Taiwan. More severe flood and drought events happen in theperiod of after 1991 than the period of 1961-1990. Frequency and duration of theflood and drought events also reveal high fluctuation. Flow regime is being alteredand is going to continue into the foreseeable future. The aquatic organisms not onlyneed to defend themselves from the anthropogenic damage to the river system butalso are facing the on-going threat from thermal and flow regime altering underchanging climate. This paper tries to raise this issue to allow water resourcesmanagers taking some precautionary measures to reduce the cumulative effects fromanthropogenic influence and changing climate.
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