Effects Of Reservoir Construction On Flow Regimes And Environmental Flow Determination In The Taizi River

Flow regime change due to reservoir construction is an important cause ofdegradation of river ecosystems. First， based upon the analysis of ecologicalsignificance of river hydrological indicators, an indicator system, which can reflect baseflow, cease to flow, high flow of Taizi River, is established together with correspondingcomputational methods for each indicator. Second, by building on the model forrelationships between flow components and the target of fish protection in Taizi River,with the hydraulic relationships between habitat indicators and flows magnitude, theenvironmental flow in three monitored sections, which consists of base flow, pulse flow,bankfull flow and overbank flow components, was estimated via FLOWS method.Through the analysis of the daily runoff data of Taizi River over a period of53years,the variations of those aforementioned hydrological indicators due to reservoirconstruction are computed, from which the following effects of reservoir construction onflow regime and ecosystem can be reflected:1） the base flow process of Taizi Riverhas been changed with a reduced base flow during flood seasons and an increased baseflow before flood seasons,2） the frequency and duration of cease to flow at LiaoyangReach has been increased,3） the frequency of floods during flood seasons has beenreduced, while the frequency and duration of small and medium-sized flow pulse eventsafter flood seasons has been increased. Results of environmental flow determinationindicated that: the annual base flow of Benxi Reach, Liaoyang Reach, Xiaolinzi Reachand Tangmazhai Reach is337million m3,337million m3,340million m3and342million m3respectively. Also, the pulse flow, bankful flow and overbank flow haverecommended in this research, which can reflect the consistency of the environmentalflow and the natural runoff process. Reservoir construction in Taizi River, which hasbeen caused a remarkable hydrologic alteration, has a negative ecological effect onriverine ecosystem. The findings therefore laid the theoretical basis for reservoirecological dispatch and river ecological restoration in Taizi River.