Water planning models are increasingly more advanced at simulating hydrology, infrastructure, and future climate pressures, yet they still often miss a critical piece of the system: how water is accessed by different groups within a watershed. This paper introduces Community-Informed Water Systems Modelling (CI-WSM), a participatory approach that co-creates modelling choices with local stakeholders so social dynamics like marginalization, cultural norms, and unequal access are reflected in how water challenges are defined and assessed.

CI-WSM is designed to be flexible and applicable to established tools such as the Water Evaluation and Adaptation Planning (WEAP) model, adding socioeconomic depth to conventional planning. The framework follows five phases: contextual analysis, co-development with stakeholders, baseline conditions integrating social and biophysical data, future resilience analysis through climate and socio-economic scenarios, and policy influence that translates results into accessible, actionable strategies aligned with planning processes.

The paper tests key elements of CI-WSM across three case studies: Marquina (Bolivia), Stung Chinit (Cambodia), and Tupiza (Bolivia). Each case builds on lessons from the previous one, showing how mixed qualitative and quantitative methods can improve model representations of water rights and system position, upstream-downstream inequities in water collection burdens, and the links between poverty and domestic and agricultural water use across rural and urban areas.

Overall, the study shows how community-informed modelling can make equity considerations operational, improve the relevance of model outputs, and strengthen locally grounded decision-making. CI-WSM is presented as a transferable approach that helps communities and institutions use shared tools and evidence to support more inclusive, resilient water management.