A. F. M. Kamal Chowdhury

There is a growing demand for time-series data on hydropower availability at the site level, particularly to enable detailed investigation of the evolving role of hydropower in power grids. Such a dataset for both existing and potential hydropower sites, with global coverage, and incorporating future uncertainty, is still not available. Here, we present HydroSMADE (Hydropower Site-level Monthly Availability Data Ensemble) v1.0, a new open dataset that provides monthly hydropower availability for 1,593 existing and 124,333 potential sites worldwide over the period 1950–2100. The dataset is generated by using a global hydrologic model (Xanthos) with explicit representation of hydropower operations. Specifically, HydroSMADE distinguishes between storage and diversion sites, applies optimized operating rules, and incorporates site-specific characteristics such as generation capacity, maximum turbine flow, and reservoir storage. Driven by bias-corrected meteorological inputs, the site-level hydropower availability data is provided for 30 alternative future scenarios. Technical validation demonstrates consistency with reference datasets and literature across spatial scales, while highlighting improvements in representing operational differences between storage and diversion sites.

Alongside other renewable energy sources, hydropower features prominently in commitments to achieve Net Zero Emissions, which could put decarbonization and freshwater biodiversity conservation goals in conflict. Here, we use multi-objective optimization to quantify tradeoffs emerging among fish biodiversity, carbon emissions and hydropower expansion across 17 river basins where hydropower will proliferate under Net Zero commitments. Project portfolios minimizing biodiversity impacts can triple carbon emission intensities in comparison to low-carbon hydropower portfolios. While carbon-biodiversity tradeoffs are inevitable, offsetting emissions from biodiversity-centered planning would only cost 0.29 U$ MWh ^-1 , or 0.45% of the levelized cost of hydroelectricity. Our analysis uncovers an opportunity to leverage the carbon market to both minimize biodiversity impacts of hydropower proliferation and minimize emissions with little loss in economic competitivity. More broadly, we provide a framework to navigate the tradeoffs among multiple ecological, economic and societal goals that are ubiquitous across many pressing sustainability challenges.

Decarbonizing power systems with high shares of solar and wind requires enhanced grid-balancing strategies. In China, current policy emphasizes deploying new coal-fired power plants to provide dispatchable flexibility, yet quantification of their effectiveness and implications relative to alternative options remains limited. Using an integrated modeling framework, we compare coal-based and alternative grid-balancing strategies for the China Southern Power Grid (CSPG) under two decarbonization pathways. We find that deploying nearly 50 GW of planned coal capacity in CSPG increases system costs by 11–19%, results in substantial underutilization of the coal assets, and delivers limited reliability benefits. In contrast, solar and wind supported by hydropower and battery storage supply most future electricity demand at lower costs, while a modest contribution of fossil-fired generators with carbon capture and storage further enhances operational efficiency by reducing battery dependence and curtailment.

Long-term planning of low-carbon electricity systems in the Global South involves deeply uncertain infrastructure investments, often undertaken independently from neighboring energy systems. In principle, national grids benefit from greater regional integration, but the nature of these benefits is sensitive to techno-economic uncertainty and natural resource distribution. We examine the value of regional electricity coordination for a South American subregion with abundant, geographically variable renewable resources, under stringent emissions reduction targets and a range of techno-economic assumptions. Results show that decarbonization is achievable with modest cost premiums, which are further mitigated by international coordination. Differences in the deployment of renewables across scenarios tend to offset at the regional level; however, variability at the country level suggests that national decarbonization pathways are sensitive to technology characteristics. Achieving mitigation goals without coordination requires additional generation capacity, at more than triple the added cost of coordinated planning scenarios (14.7-22.8 vs. 3.5-7.0 billion USD). Beyond South America, these results are relevant to regions looking to meet emissions targets through greater international cooperation.

Long-term planning of low-carbon electricity systems in the Global South involves deeply uncertain infrastructure investments, often undertaken independently from neighboring energy systems. In principle, national grids benefit from greater regional integration, but the nature of these benefits is sensitive to techno-economic uncertainty and natural resource distribution. We examine the value of regional electricity coordination for a South American subregion with abundant, geographically variable renewable resources, under stringent emissions reduction targets and a range of techno-economic assumptions. Results show decarbonization is achievable with modest cost premiums which are further mitigated by international coordination. Differences in renewables deployment across scenarios tend to offset system-wide; however, country-level variability suggests national decarbonization pathways are sensitive to technology characteristics. Achieving mitigation goals without coordination requires additional generation capacity, at more than triple the added cost of coordinated planning scenarios ($14.7-22.8B vs. $3.5-7.0B). Beyond South America, these results are relevant to regions looking to meet emissions targets through greater international cooperation.

Reservoirs play a significant role in modifying the spatiotemporal availability of surface water to meet multi-sector human demands, despite representing a relatively small fraction of the global water budget. Yet the integrated modeling frameworks that explore the interactions among climate, land, energy, water, and socioeconomic systems at a global scale often contain limited representations of water storage dynamics that incorporate feedbacks from other systems. In this study, we implement a representation of water storage in the Global Change Analysis Model (GCAM) to enable the exploration of the future role (e.g., expansion) of reservoir water storage globally in meeting demands for, and evolving in response to interactions with, the climate, land, and energy systems. GCAM represents 235 global water basins, operates at 5-year time steps, and uses supply curves to capture economic competition among renewable water (now including reservoirs), non-renewable groundwater, and desalination. Our approach consists of developing the GLObal Reservoir Yield (GLORY) model, which uses a linear programming (LP)-based optimization algorithm and dynamically linking GLORY with GCAM. The new coupled GCAM–GLORY approach improves the representation of reservoir water storage in GCAM in several ways. First, the GLORY model identifies the cost of supplying increasing levels of water supply from reservoir storage by considering regional physical and economic factors, such as evolving monthly reservoir inflows and demands, and the leveled cost of constructing additional reservoir storage capacity. Second, by passing those costs to GCAM, GLORY enables the exploration of future regional reservoir expansion pathways and their response to climate and socioeconomic drivers. To guide the model toward reasonable reservoir expansion pathways, GLORY applies a diverse array of feasibility constraints related to protected land, population, water sources, and cropland. Finally, the GLORY–GCAM feedback loop allows evolving water demands from GCAM to inform GLORY, resulting in an updated supply curve at each time step, thus enabling GCAM to establish a more meaningful economic value of water. This study improves our understanding of the sensitivity of reservoir water supply to multiple physical and economic dimensions, such as sub-annual variations in climate conditions and human water demands, especially for basins experiencing socioeconomic droughts.

Decarbonizing the electricity sector requires massive investments in generation and transmission infrastructures that may impact both water and land resources. Characterizing these effects is key to ensure a sustainable energy transition. Here, we identify and quantify the unintended consequences of decarbonizing the China Southern Power Grid, China’s second-largest grid. We show that reaching carbon neutrality by 2060 is feasible; yet, doing so requires converting 40,000 square kilometers of land to support solar and wind as well as tapping on rivers to build ~32 gigawatts of hydropower. The impact of wind and solar development would span across multiple sectors, since crop and grassland constitute 90% of the identified sites. The construction of new dams may carry major externalities and trickle down to nearby countries, as most dams are located in transboundary rivers. Curbing the international footprint of this decarbonization effort would require additional investments (~12 billion United States dollars) in carbon capture technologies.

The scale at which low-carbon electricity will need to be deployed to meet economic growth, electrification, and climate goals in Africa is unprecedented, yet the potential land use and freshwater impacts from this massive build-out of energy infrastructure is poorly understood. In this study, we characterize low-impact onshore wind, solar photovoltaics, and hydropower potential in Southern Africa and identify the cost-optimal mix of electricity generation technologies under different sets of socio-environmental land use and freshwater constraints and carbon targets. We find substantial wind and solar potential after applying land use protections, but about 40% of planned or proposed hydropower projects face socio-environmental conflicts. Applying land and freshwater protections results in more wind, solar, and battery capacity and less hydropower capacity compared to scenarios without protections. While a carbon target favors hydropower, the amount of cost-competitively selected hydropower is at most 45% of planned or proposed hydropower capacity in any scenario—and is only 25% under socio-environmental protections. Achieving both carbon targets and socio-environmental protections results in system cost increases of 3-6%. In the absence of land and freshwater protections, environmental and social impacts from new hydropower development could be significant.