In Central Asia, the Amu Darya and Syr Darya are more than rivers: they are the operating backbone of water security, agricultural production, reservoir management and hydropower (HP) generation across the Aral Sea Basin. Within the Hydro4U project, CARTIF has developed a system dynamics model to assess Water–Energy–Food (WEF) Nexus interactions [1]. In the model, climate was incorporated as an exogenous variable through the combined SSP/RCP scenarios, namely SSP1-2.6 (low-emission pathway), SSP2-4.5 (intermediate-emission pathway), and SSP5-8.5 (high-emission pathway) [2]. Although recent ScenarioMIP–CMIP7 literature indicates that SSP5-8.5 is increasingly implausible for the 21st century due to renewable energy cost trends, emerging climate policies, and recent emissions trajectories [3], it was retained in the model as a stress-test scenario alongside the more plausible low- and medium-emission futures. A key innovation of the WEF Nexus model is that it does not treat the Amu Darya and Syr Darya as uniform systems, but instead identifies hydrological changes at sub-basin resolution, covering 19 sub-basins in the Amu Darya and nine in the Syr Darya. This represents an important methodological advance: it supports more targeted reservoir planning, small HP assessment and transboundary coordination, while helping decision-makers understand how local hydrological changes can propagate across the wider WEF Nexus.

The integration of SSP/RCP scenarios into the WEF Nexus model enables a detailed assessment of how precipitation-driven water availability may evolve across the Aral Sea Basin. The model results indicate that annual water availability remains relatively stable in the Region under the three scenarios at basin scale through 2050, with only minor interannual fluctuations in both river systems. Under SSP1-2.6, both the Amu Darya and Syr Darya show a slight decrease by 2050 compared with 2020, close to 0.1%. Under SSP2-4.5, the pattern is essentially stable, while SSP5-8.5 shows small increases in both basins. However, this apparent stability should not be interpreted as absence of risk. Even modest shifts in precipitation timing, runoff generation and storage conditions can affect river regulation, reservoir inflows and seasonal water allocation, especially in a region where HP releases, irrigation demand and downstream ecosystem needs are tightly interconnected.

The implications of these climate scenarios for HP were also assessed, showing that their impacts are predominantly operational. Hydroelectric generation in both basins depends not only on annual water volumes, but also on when water reaches reservoirs, how much can be stored, and how releases are coordinated between upstream and downstream users. The simulations show a gradual increase in modelled HP production toward 2050 in both basins, with the Amu Darya showing a stronger increase than the Syr Darya. This suggests that, under the simulated assumptions, the resource base for HP remains viable. Nevertheless, reservoirs may face increasing pressure to provide multiple services simultaneously: winter energy supply, summer irrigation releases, flood buffering, ecological flows and long-term storage security. The Syr Darya is particularly sensitive because upstream HP production and downstream irrigation demand often peak in different seasons. If precipitation patterns become more variable, reservoir operation will need to become more flexible and more coordinated. In the Amu Darya, larger basin size and higher water availability provide a stronger buffer, but the basin also supports extensive irrigated agriculture, which can intensify competition for stored water during dry years.

As climate uncertainty grows, integrated WEF Nexus modelling offers a pathway to anticipate risks, reduce tensions and support a more resilient future for the rivers and communities of Central Asia.

AI was used to support the creation of the figures

Authors and Picture credits (with graphical AI support): Sara Pérez Pérez (sarper@cartif.es) and Raquel López (raqlop@cartif.es)

Website: www.cartif.es

Twitter: @CARTIFCT

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References:

[1] Pérez Pérez,S.; Ramos-Diez,I.; López Fernández,R. Transboundary Water–Energy–Food Nexus Management in Major Rivers of the Aral Sea Basin Through System Dynamics Modelling. Water2025,17, 2270. https://doi.org/10.3390/w17152270

[2] Service CCC. CMIP6 Climate Projections. 2020. Available online: https://www.wdc-climate.de/ui

[3] Van Vuuren, D. P., O’Neill, B. C., Tebaldi, C., Sanderson, B. M., Chini, L. P., Friedlingstein, P., Hasegawa, T., Riahi, K., Govindasamy, B., Bauer, N., Eyring, V., Fall, C. M. N., Frieler, K., Gidden, M. J., Gohar, L. K., Högner, A., Jones, A. D., Kikstra, J., King, A., Knutti, R., Kriegler, E., Lawrence, P., Lennard, C., Lowe, J., Mathison, C., Mehmood, S., Nicholls, Z., Prado, L. F., Zhang, Q., Rose, S. K., Ruane, A. C., Sandstad, M., Schleussner, C.-F., Seferian, R., Sillmann, J., Smith, C., Sörensson, A. A., Panickal, S., Tachiiri, K., Vaughan, N., Vishwanathan, S. S., Yokohata, T., Zecchetto, M., and Ziehn, T.: The Scenario Model Intercomparison Project for CMIP7 (ScenarioMIP-CMIP7), Geosci. Model Dev., 19, 2627–2656, https://doi.org/10.5194/gmd-19-2627-2026, 2026

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