Non-deterministic multi-level model for planning water-ecology nexus system under climate change

Water scarcity and ecological degradation impede sustainable development in Central Asia, which urgently calls for synergistic planning of water-ecology (WE) nexus system. However, existing management models may have large uncertainties, restricting their effectiveness. Here, we develop a copula-based flexible fuzzy multi-level programming (CFMP) method, which tackles uncertainties, such as water demands, and balances trade-offs among competing managers in top-down decision-making processes. Next, we formulate a CFMP-WE model for Central Asia (2021–2050), considering objectives of economic development, food security, and ecological restoration, and design 243 planning scenarios. We found that ecological water allocation would account for 5.9%–12.2% to support sustainable development; however, policymakers need to reduce agricultural water allocation, forgoing 7.8%–20.1% of the system benefit (i.e., economic benefit for WE nexus system). Agricultural water use would still be the largest (with 25.6%–29.4% for cereal crops to ensure food security), but its share would decline to conserve water for users like industry.