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China is the world’s top water consumer and CO2emitter. The government has deployed Three Red Lines (TRLs) to improve water security by 2030 and committed to achieving carbon neutrality by 2060. China’s industries, which account for half of national CO2emissions and >20% water withdrawals, is key to decarbonization and water conservation. However, there remains a lack of consensus regarding whether industrial emission reduction and water saving can be achieved simultaneously. Here, we adopt a general equilibrium model using a self-developed high-resolution provincial water-use inventory based on enterprise census data, to uncover the impacts achieving carbon neutrality would have on industrial water use across China. Meeting carbon neutrality enables the achievement of the TRL-associated industrial water-use target and can reduce industrial water use by 24% in 2060. Nevertheless, if inter-provincial industrial relocation occurs, water use could rise in certain provinces, reducing the above water-saving potential. Stricter and coordinated policies and technological advancements are essential to successfully address climate and water challenges concurrently.

The development of and access to freshwater resources in East Africa is fundamental to the region's sustainable development goals. Following vision documents for regional development and working with local stakeholders, we developed water scenarios up to 2050 that inform the hydro-economic modeling analysis of the extended Lake Victoria Basin, the headwaters of the Nile River. Water scenarios that take an integrated approach to assessing the combined effects of climate change, land use, and increasing human water use suggest that the flow regime of the Nile may remain relatively stable. However, if this stability is to be achieved, while at the same time sufficient water is preserved for healthy freshwater ecosystems, a large fraction of water infrastructure must rely on advanced, often costly technologies and management. Interconnected analyses of both upstream and downstream water resources over time, guided by co-developed scenarios, are indispensable for planning sustainable water-development pathways.

Worldwide hundreds of millions of people suffer from water, food and energy insecurity in transboundary river basins, such as the Zambezi River Basin. The interconnected nature of nexus is often not recognized in investment planning and many regional policymakers lack adequate tools to tackle it. Future growing demands and climate change add an additional challenge. In this study, we combine policy relevant co-developed stakeholder scenarios and integrated nexus modeling tools to identify key solutions to achieve sustainable development in the Zambezi. Results show that siloed development without coordination achieves the least economic and social benefits in the long term. Prioritizing economic benefits by maximizing the use of available natural resources results in the expansion of irrigated areas by more than a million hectares and increase in hydropower production by 22,000 GWh/year in the coming decades, bringing significant economic benefits, up to $12.4 billion per year, but causes local water scarcity and negative impacts on the environment. Combining environmental protection policies with sustainable investments of $7.2 billion per year (e.g. groundwater pumping and wastewater treatment and reuse, irrigation efficiency improvements, and farmer support aimed to improve food security and productivity) results in significantly higher social benefits with economic benefits that still reach $11.3 billion per year.

This study presents the development of a new bottom‐up large‐scale hydroeconomic model, Extended Continental‐scale Hydroeconomic Optimization (ECHO), that works at a subbasin scale over a continent. The strength of ECHO stems from the integration of a detailed representation of local hydrological and technological constraints with regional and global policies, while accounting for the feedbacks between water, energy, and agricultural sectors. In this study, ECHO has been applied over Africa as a case study with the aim of demonstrating the benefits of this integrated hydroeconomic modeling framework. Results of this framework are overall consistent with previous findings evaluating the cost of water supply and adaptation to global changes in Africa. Moreover, results provide critical assessments of future investment needs in both supply‐ and demand‐side water management options, economic implications of contrasting future socioeconomic and climate change scenarios, and the potential trade‐offs among economic and environmental objectives. Overall, this study demonstrates the capacity of ECHO to address challenging research questions examining the sustainability of water supply and the impacts of water management on energy and food sectors and vice versa. As such, we propose ECHO as useful tool for water‐related scenario analysis and management options evaluation. A new large‐scale hydroeconomic model (ECHO) is developedECHO is used to evaluate the water management adaptation pathways in Africa under various socioeconomic and climate futuresFuture scenario simulations highlight the capacity of ECHO to address challenging research questions related to water‐energy‐land nexus

This study develops a hydro-economic model for the coastal aquifer Mahdia Ksour Essef in Tunisia in order to analyze how external shocks (climate change, energy price increase) and management policies can affect groundwater sustainability during the coming decades. Twenty-one scenarios covering three management policies (free market, partial cooperation, and full cooperation policy) under various potential climate and economic changes are evaluated. The results of scenario simulations show the potential impact of energy soaring prices and climate change on the aquifer’s water table level, groundwater extractions, cropland areas, and farmers’ benefits under each policy option in the future. They also show that the best scenario to address the effects of climate change would need to take into account environmental externalities and efficient energy prices. The findings of this study are very important in the context of climate change and uncertain global energy markets and provide feasible alternatives to preserve the regional economy and aquifer sustainability.

Sustainable water management is challenging because of the wide range of agents who need water and the different kinds of use, in a context of limited water availability. The availability of water for use, at a given point in time and space, depends on numerous physical and climatic variables, as well as upstream uses and downstream commitments. Therefore, any analysis of water use and management must inevitably be made in the context of such variability. This paper develops an integrated, multiregional, hydro-economic modeling framework to analyze the spatial and temporal dependencies between economic agents in the different regions and areas of a river basin. We combine hydro-economic modeling (partial economic equilibrium) and a multiregional input–output model (general equilibrium) to take advantage of both methodologies. Spatial variability is considered in the input–output models, but variability in both time and space is also considered by the hydro-economic model. Hydro-economic models are used to quantify direct impacts, but not indirect impacts in some specific sectors of the economy, while the input–output model reveals the relationships between all sectors and regions, and facilitates the assessment of total impacts (direct plus indirect) of a range of scenarios. While the methodology described in this paper is applicable to any river basin, the case study considered is the Ebro River Basin, in Spain. To show the potential of the modeling framework, two scenarios are simulated to assess the impacts on water use, value added, and jobs across scales. The results of these scenarios show that decreases in water availability have negative impacts on socio-economic variables (value added and employment). The trade-off between water availability and socio-economic variables depends on the temporal and spatial variability of the resource, and affects each location in the basin in a different way, demonstrating the importance of the methodology developed.

Hydro-economic modeling (HEM) addresses research and policy questions from socioeconomic and biophysical perspectives under a broad range of water-related topics. Applications of HEM include economic evaluations of existing and new water projects, alternative water management actions or policies, risk assessments from hydro-climatic uncertainty (e.g., climate change), and the costs and benefits of mitigation and/or adaptation to such events. This paper reviews applications of HEM in five different categories: (1) climate change impacts and adaptation, (2) water–food–energy–ecosystems nexus management, (3) capability to link to other models, (4) innovative water management options, and (5) the ability to address and integrate uncertainty. We find that (i) the increasing complexity and heterogeneity of water resource management problems due to the growing demand and competition for water across economic sectors, (ii) limited availability and high costs of developing additional supplies, and (iii) emerging recognition and consideration of environmental water demands and value, have inspired new integrated hydro-economic problems and models to address issues of water–food–energy nexus sustainability, resilience, reliability through water (re)allocation based on the relative “value” of water uses. In the past decade, the field of HEM has improved the integration of ecosystem needs, but their representation is still insufficient and mostly ineffective. HEM studies address how to sustainably manage water resources, including groundwater which has become an area of particular interest in climate change adaptation. The current most used spatial and temporal resolutions (basin-scale and yearly time-step) are appropriate for planning but not for operational decisions and could be underestimating impacts from extreme events (e.g., flood risk) captured only by sub-monthly time scales. In addition, HEM primarily focuses on biophysical and economic indicators but often overlooks preferences and perspectives of stakeholders. Lastly, HEM has been widely used to analyze transboundary cooperation, showing benefits for increasing water security and economic development, particularly as climate change develops. We conclude that the field of HEM would benefit from developing more operational models and enhancing the integration of commonly neglected variables, such as social equity components, ecosystem requirements, and water quality.