Assessment of Karkheh Dam Impacts on Ecohydrological Downstream Conditions in Southwest of Iran

Dams can change the natural flow of the rivers through influencing the total flow rate, the quality of water, the seasonal scheduling of the flow, continuing the flow, and hydrologic occurrences. Alteration in streamflow regimes may modify many of these attributes and impair ecosystem connectivity. This paper presents assessment of hydrologic alteration at the Payepol streamgauge site to demonstrate the influence of Karkheh Dam on ecohydrological downstream condition using Indicators of Hydrologic Alteration and Range of Variability Approach methods. The results indicate that Karkheh Dam have greatly altered the natural flow regime, range condition and spatial variability. The 31 hydrological indexes have completely changed during 35 years of before constructing of the dam over Karkheh River, particularly in downstream, and regarding the ranges of variability achieved from the period of before constructing the dam . The river ecohydrological targets and minimum ecological and environmental flow requirements for downstream of Karkheh Dam defined by this study can support ecosystem management and restoration plans and provide ecological operations for the Khuzestan Province.