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Abstract. The densely populated plains of the lower Indus Basin largely depend on water resources originating in the mountains of the transboundary upper Indus Basin. Recent studies have improved our understanding of this upstream–downstream linkage and the impact of climate change. However, water use in the mountainous part of the Indus and its hydropolitical implications have been largely ignored. This study quantifies the comparative impact of upper Indus water usage, through space and time, on downstream water availability under future climate change and socio-economic development. Future water consumption and relative pressure on water resources will vary greatly across seasons and between the various sub-basins of the upper Indus. During the dry season, the share of surface water required within the upper Indus is high and increasing, and in some transboundary sub-basins future water requirements exceed availability during the critical winter months. In turn this drives spatiotemporal hotspots to emerge in the lower Indus where seasonal water availability is reduced by over 25 % compared to natural conditions. This will play an important, but previously unaccounted for, compounding role in the steep decline of per capita seasonal water availability in the lower Indus in the future, alongside downstream population growth. Increasing consumption in the upper Indus may thus locally lead to water scarcity issues, and increasingly be a driver of downstream water stress during the dry season. Our quantified perspective on the evolving upstream–downstream linkages in the transboundary Indus Basin highlights that long-term shared water management here must account for rapid socio-economic change in the upper Indus and anticipate increasing competition between upstream and downstream riparian states.

We present a systematic framework to assess sustainable hydropower potential. • The framework assesses theoretical, technical, economic, and sustainable potential. • It combines 30 datasets to represent natural, legal, disaster and social constraints. • Including these constraints in early assessments can improve hydropower decisions • The framework helps balance SDG7 (energy) with the linked SDGs 2 & 6 (food, water).

Water security and food security in the Indus basin are highly interlinked and subject to severe stresses. Irrigation water demands presently already exceed what the basin can sustainably provide, but per-capita food availability remains limited. Rapid population growth and climate change are projected to further intensify pressure on the interdependencies between water and food security. The agricultural system of the Indus basin must therefore change and adapt to be able to achieve the associated Sustainable Development Goals (SDGs). The development of robust policies to guide such changes requires a thorough understanding of the synergies and trade-offs that different strategies for agricultural development may have for water and food security. In this study, we defined three contrasting trajectories for agricultural system change based on a review of scientific literature on regional agricultural developments and a stakeholder consultation workshop. We assessed the consequences of these trajectories for water and food security with a spatially explicit modeling framework for two scenarios of climatic and socio-economic change over the period 1980–2080. Our results demonstrate that agricultural system changes can ensure per capita food production in the basin remains sufficient under population growth. However, such changes require additional irrigation water resources and may strongly aggravate water stress. Conversely, a shift to sustainable water management can reduce water stress but has the consequence that basin-level food self-sufficiency may not be feasible in future. This suggests that biophysical limits likely exist that prevent agricultural system changes to ensure both sufficient food production and improve water security in the Indus basin under strong population growth. Our study concludes that agricultural system changes are an important adaptation mechanism toward achieving water and food SDGs, but must be developed alongside other strategies that can mitigate its adverse trade-offs.

Skillful weather and seasonal predictions have considerable socio-economic potential and could provide meaningful information to farmers and decision-makers towards agricultural planning and decision-making. Peri-urban farmers in the Lower Ganges Delta need skillful forecast information to deal with increased hydroclimatic variability. In the current study, verification of European Centre for Medium-Range Weather Forecasts’ System 5 (ECMWF SEAS5) seasonal prediction system is performed against ground observations for the Lower Ganges Delta using three skills assessment metrics. Additionally, meteoblue hindcasts are verified for Khulna station according to the peri-urban farmers’ needs and an assessment of onset/offset dates of rainy season is also conducted using the same ground observations. The results indicated that the skill of both examined products is limited during the pre-monsoon and monsoon periods, especially in the west side of the Bay of Bengal. However, during the dry winter season, skill is high, which could lead to potential agricultural benefits concerning irrigation planning. Interannual variability and trend indicated that onset dates have become later and that the length of the rainy season reduced. This could increase the pressure on the already challenging situation the farmers are experiencing, in relation to hydro-climatic variability.