Sustainable management of water-economy-ecology nexus through coupling bi-level fractional optimization with effluent-trading mechanism: A case study of Dongjiang watershed

• Published in: Ecological indicators Vol. 154; p. 110752
• Main Authors: Zhang, Y.F., Li, Y.P., Huang, G.H., Ma, Y.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.10.2023; Elsevier
• Subjects: Bi-level programming; Effluent trading; Fractional programming; Uncertainty; Water-economy-ecology nexus; Watershed sustainability; Uncertainty; Water-economy-ecology nexus; Bi-level programming; Effluent trading; Fractional programming; Watershed sustainability
• ISSN: 1470-160X; 1872-7034
• DOI: 10.1016/j.ecolind.2023.110752

•A novel optimization model is proposed for water-economy-ecology nexus system.•The developed model can address bi-level ratio-objectives under uncertainty.•Effluent trading is integrated into the model for pollution control.•Marginal benefit can be improved with pollutant reduction under trading mechanism.•Tradeoff between ecosystem conservation and economic development can be balanced. Ecosystem deterioration and freshwater depletion due to population growth and rapid urbanization have posed great challenges in managing water-economy-ecology nexus (WEEN) for watersheds. The objective of this study is to develop a bi-level fuzzy fractional programming (BFFP) method to identify sustainable watershed WEEN strategies with considering effluent-trading program. The BFFP method improves traditional methods for WEEN management over handling the bi-level decision process, ratio-objectives and fuzzy environmental policies simultaneously. Then, through coupling BFFP with effluent-trading mechanism, a BFFP-WEEN model is firstly formulated and employed to the Dongjiang watershed in China, where ninety-nine scenarios are examined to reflect various policy implications and decision-makers’ preferences. Major findings are: (1) compared with non-trading, effluent-trading can effectively reduce pollution discharges (e.g., reducing 140.1×106 ton of Chemical Oxygen Demand and 79.5×106 ton of Ammonia-Nitrogen over the planning horizon), revealing that effluent-trading mechanism is beneficial to the improvement of ecological environment; (2) under the trading mechanism, trading ratio has significant effects on marginal benefit and water allocation (e.g., improving marginal benefit by 15.4% and saving 363.7×106 m3 of total water allocation under 1.03 of trading ratio); (3) in order to alleviate the deterioration of ecosystem, industrial water use should be limited firstly and the area of forest land should be expanded; for ensuring the ecosystem requirements, it is recommended to promote the reuse of reclaimed water and improve wastewater treatment/recycling technology. The major improvements in this study include: (1) the development of the BFFP approach to deal with hierarchical decision conflicts and optimize system efficiency under uncertain environmental policies, and (2) the application of BFFP-WEEN model with coupling the effluent-trading mechanism to generate desired strategies for synergistic management of WEEN, and help balance the conflicts among water shortage, ecological degradation, and economic development in watersheds.