This study evaluates the environmental impacts of the Anahita Dam in Kermanshah Province, comparing the efficacy of the “Modified ICOLD” and “Iranian Leopold” matrix methods. Two scenarios - “with-project” and “no-action” - were analyzed during the construction and operation phases across three domains: physical-chemical, ecological-biological, and socio-economic-cultural environments. Under the Modified ICOLD method, the “with-project” alternative yielded a net weighted impact score of +157.6 compared to -186.6 for the “no-action” alternative, demonstrating the environmental and developmental viability of dam construction. Similarly, the Iranian Leopold Matrix revealed that despite moderate negative impacts during the construction phase, average impacts across all environments became positive during the operation phase, with no component exceeding critical thresholds. During construction, temporary and localized negative impacts were observed, most notably on river morphology, slope stability, dust generation, and natural habitats. In this phase, river morphology (scoring -5) was identified as the sole critical component; however, the remaining impacts were deemed controllable through mitigation measures. During the operation phase, the project’s positive contributions -including water resource management, flood control, microclimate improvement, agricultural development, job creation, increased land value, and tourism- significantly outweigh the negative consequences. Both methodologies confirmed the superiority of the “with-project” alternative over the “no-action” scenario. While the Modified ICOLD matrix proved more effective in temporal differentiation and impact durability, the Iranian Leopold matrix provided a more streamlined framework for rapid comparative summaries. Consequently, the construction of the Anahita Dam is justified within a sustainable development framework, provided that an Environmental Management Plan (EMP) is established, environmental flow requirements are secured, and rigorous monitoring of water quality, sedimentation, and socio-ecological indicators is implemented.