Potential impacts to freshwater ecosystems caused by flow regime alteration under changing climate conditions in Taiwan

Observed increases in the Earth's surface temperature bring with them associated changes in precipitation and atmospheric moisture that consequentially alter river flow regimes. Climate-induced flow regime changes are examined using the Indicators of Hydrologic Alteration. This article uses observed daily streamflow data to examine the flow regime alteration and how these changes might potentially affect freshwater ecosystems. Flow data from 23 gauging stations throughout Taiwan show that the annual extreme water conditions (1-, 3-, 7-, 30-, 90-day annual minima or maxima) have increased alteration compared to baseline periods (1961-1990). Specifically, more severe flood and drought events occur in the period after 1991 than the period from 1961 to 1990. The frequency and duration of flood and drought events also show increased fluctuation. Flow regimes are currently being altered by stressors that will continue into the foreseeable future and it is also happing elsewhere in the world. Aquatic organisms not only need to defend themselves from anthropogenic damage to the river system, but also face the on-going threat from climate change-induced thermal and flow regime alteration. This article raises this issue so that water resources managers may identify precautionary measures that reduce the cumulative effects of both anthropogenic flow alteration and changing climate conditions.