Ecological and economic evaluation of reservoir-based water transfer using system dynamics

To systematically evaluate the combined impact of water diversion projects on regional ecological‒economic systems, this study uses the water diversion area of ​​the Badi Reservoir in Danba County, Sichuan Province, as the research object and constructs a dynamic simulation model including water resource scheduling, ecological restoration, industrial development and policy intervention mechanisms on the basis of the system dynamics method. Focusing on core variables such as reservoir water storage, fish resources, and soil erosion intensity, four types of policy scenarios are set—the S0 baseline scenario, S1 ecological compensation enhancement scenario, S2 industrial structure synergy scenario and S3 economic synergy scenario—to simulate and analyze the regulatory effects of policy combinations on the evolutionary path of regional water-ecological-economic systems. The results show that (1) in the S0 scenario, the system's natural evolution capacity is limited, fish resources recover slowly, soil erosion persists, and the water diversion effect is not fully released; (2) although the S1 ecological compensation scenario effectively improves vegetation restoration and soil and water conservation by improving the compensation standard and suppresses the trend of soil erosion in the short term, the effect on fish resource recovery and industrial support is limited; (3) the S2 industrial synergy scenario indirectly improves ecosystem pressure while optimizing the employment structure of the tertiary industry, showing the adaptive path characteristics of medium-term industry‒ecology coordination; and (4) the S3 economic synergy scenario has the best overall performance. While enhancing fishery output and improving the output value of primary industry and forestry, this scenario achieves systematic synergy by increasing reservoir water volume, restoring fish resources and alleviating soil erosion.