A transboundary water allocation strategy for the Aral Sea Basin: Integrating the water-food-energy-environment nexus

Public summary

* Coupling conventional reservoirs with seasonal pumped hydropower storage helps alleviate water competition.

* Water allocation optimization achieved relative equity (Gini < 0.29), balancing food, hydropower, and ecology.

* Trade-offs exist between benefits and water equity, while benefits are related to greenhouse gas emissions.

Abstract

Water resource competition has disrupted sustainable development in the Aral Sea Basin, necessitating integrated strategies for the water-food-energy-environment nexus to address challenges from ongoing climate change, ecological restoration, growing food demand, and potential hydropower projects impacting water stability. This study developed a multi-objective optimization model to address these issues. Results showed relatively equitable water allocation, with Gini coefficients consistently below 0.29 across all scenarios. Agricultural water use ranged from 71.71 to 80.53 × 109 m3, while seasonal pumped hydropower storage reservoirs increased upstream controllable water to 42.91–58.47 × 109 m3 (35%–44%). Hydropower remained stable owing to reservoir coordination. However, to ensure ecological flows (35.38–37.78 × 109 m3), crop areas should be reduced by 14.37%–21.05% under SSP2-4.5 and 16.16%–23.93% under SSP5-8.5. A trade-off emerged between benefits and water allocation equity, particularly in high-emission, low-inflow scenarios, alongside a positive correlation between benefits and greenhouse gas emissions. These findings emphasize the critical need for integrated management of the Aral Sea Basin’s interconnected resource systems.

The 2030 global agenda for Sustainable Development Goals (SDGs) focused on the escalating crisis for resource security. Growing populations, urbanization, and climate change are increasing the demand for essential resources such as water, energy, and food, leading to their rapid depletion and compromising the critical interdependencies among them. Notably, global water demand, primarily for food and energy production, is projected to increase by 20%–30% by 2050, reaching 5,500−6,000 km3 annually, far exceeding the current near-sustainable withdrawal of 4,600 km3. These interdependencies often create complex trade-offs, particularly at the river basins scale, where upstream regions often increase reservoir storage during summer for winter hydropower generation. This practice reduces the downstream irrigation supply causing seasonal water shortages and increased winter flood risk. Such imbalances in allocation exacerbate water scarcity, which already affects around 3.2 billion people, and contribute to estimated annual losses of $23.8 billion.