Ecologically based methods for multi-objective water resources management in Taiwan

Water resources planning and management activities have expanded from a narrow focus on structural solutions to flood defense and point source treatments that address water quantity. This expansion has led to a more holistic management approach that better addresses watershed scale problems and integrates ecosystem needs with management protocols. A common feature of holistic management is naturalization, which is intended to take advantage of natural processes to meet management goals by returning modified ecosystem conditions to a more natural state. In water resources management, naturalization has focused on reservoir management, diversion control, and alteration of channel structure to produce what is termed the "natural flow regime." The natural flow regime can either mimic historical conditions or meet flow quantity and variability targets to support a self-sustaining ecosystem. It integrates ecological, geomorphic, and hydrologic functions in a watershed and provides a regime-based approach to meeting naturalization objectives.; This study has constructed a fish autecology matrix that considers physical habitat, spawning, ecological issues, water quality issues, and human values for Northern Taiwan. By using the matrix analysis method, fish community habitat requirements can be identified. The Taiwan Ecohydrology Index System (TEIS) has been developed by adding species habitat and ecological needs of fish communities to hydrological statistics to analyze flow requirements. This analysis is then used to develop indicators of an ecological flow regime that considers natural flow variability with species habitat and ecological needs to provide guidance in the management of the volume, frequency and timing of flows. The multi-objective model uses the ecological flow regime as the ecosystem needs objective and combines it with consideration of human needs to find solutions that can satisfy both ecosystem and human water needs.