Climate change is known to worsen conflicts, but its combination with other factors affecting water-related conflicts remains less explored. Using a scoping review, this study examined research in the climate-water-conflict nexus. The analysis identified key research gaps, priorities, and differences and similarities in studies across different regions. Most studies focused on Asia and Africa, with few exploring other parts of the world. Governance and livelihoods emerged as significant factors in water-related conflict responses worldwide, with responses varying across regions. For instance, farmer-herder conflicts were common in Africa, while agriculture was more related to governance and water management in Asia. Research priorities forward should diversify the range of studied water-related conflict subjects and regions and give special focus to regions vulnerable to hydroclimatic change. More focus on cooperation and non-violent conflicts is also vital for understanding and being able to project and mitigate future water-related conflict responses to climate change.

Population growth is increasing the pressure on water resource availability. For useful assessment and planning for societal water availability impacts, it is imperative to disentangle the direct influences of human activities in the landscape from external climate-driven influences on water flows and their variation and change. In this study we used the water balance model, a gridded global hydrological model, to quantify and distinguish human-driven change components, modified by interventions such as dams, reservoirs, and water withdrawals for irrigation, industry, and households, from climate-driven change components on four key water balance variables in the terrestrial hydrological system (evapotranspiration, runoff, soil moisture, storage change). We also analyzed emergent effect patterns in and across different parts of the world, facilitating exploration of spatial variability and regional patterns on multiple spatial scales, from pixel to global, including previously uninvestigated parts of the world. Our results show that human activities drive changes in all hydrological variables, with different magnitudes and directions depending on geographical location. The differences between model scenarios with and without human activities were largest in regions with the highest population densities. In such regions, which also have relatively large numbers of dams for irrigation, water largely tends to be removed from storage and go to feed increased runoff and evapotranspiration fluxes. Our analysis considers a more complete set of hydrological variables than previous studies and can guide further research and management planning for future hydrological and water availability trends, including in relatively data-poor parts of the world.

Despite strong interest and conflict research spanning multiple disciplines, connections between water flows and conflicts remain unclear, due to incomplete datasets on water-related conflict-cooperation events and poor understanding of socioeconomic and biophysical causes of such conflicts. The dataset on water-related conflict-cooperation events compiled in this study extends to 2019, updating previous datasets that covered only up to 2008, yielding important new insights on cooperation-conflict trends. Global and regional trends were analyzed using the new events dataset, together with changes in hydroclimatic variables and population density. The analysis revealed that water-related cooperation was far more common than conflicts across all regions, in both drier and wetter climates, indicating that abundance and lack of water can both promote cooperation. However, conflict events were more common in drier climates where water is scarcer. This cooperation-conflict balance shifted in the 2000s, with conflict events increasing, to outnumber cooperation events in 2017. The main shift occurred in Africa and Asia, where increased conflicts in Africa coincided with a prolonged period of below-average precipitation and severe drought, while the shift in Asia coincided with increased evapotranspiration caused by human activities and increased population density. Differences between regions were confirmed by event descriptions, with events in Africa relating to water access and farmer-herder conflicts, and events in Asia relating to irrigation and dam construction. These differences highlight the need for regional-scale analysis of water-related conflict-cooperation trends and pathways. With climate change and human activities expected to increase, the increasing trend in conflict events could persist, with water resources becoming a more frequent cause of future conflict. Identifying these complex cooperation-conflict changes is vital in determining future actions required to reduce conflict events and promote cooperation on water.

The demand for water is increasing rapidly due to growing populations and intensified human activities such as agriculture, industry, and energy production. This has led to increasing concerns about the availability and sustainable use of freshwater, as conflicts over water are reported to have increased while cooperation has declined over the past decade. Further research on water-related conflict and cooperation is needed to improve understanding of key factors and ways to mitigate the conflicts and counteract their escalating trend. This study investigates which main factors relate to and may have affected cooperation and conflict events worldwide in the last 70 years as a basis for understanding how to promote effective water-based cooperation and conflict reduction; investigated factors include, for example, hydro-climatic and socioeconomic ones, with the latter encompassing, e.g., wealth, export dependency, demographic, and water use factors. The study used panel data models and content analysis of reported event descriptions to achieve its aims of identifying main conflict-influencing factors and which of these may contribute to successful conflict mitigation. The results indicate that countries that cooperate experience significant subsequent decrease in conflicts. Cooperation is particularly effective in areas with low water stress, while in high-stress areas, diplomatic efforts combined with economic collaboration can boost resilience and increase conflict resolution effectiveness. Economic robustness and trade incentives to maintain peace are strongly correlated with fewer conflicts. Cooperation with less affluent countries also emerges as influential for fewer conflicts, and stability or even growth in GDP and exports. Cooperation efforts can thus be strategic investments for promoting diplomatic stability and improving a nation's economic standing. Understanding which measures can be successful for conflict mitigation can provide valuable insights to global policymakers and water management leaders, enabling them to avoid future conflicts based on current and projected water availability.