OpenMap Development Tanzania (OMDTZ) undertook a participatory mapping initiative in the Weruweru River Catchment, Kilimanjaro region, to enhance sustainable water management through detailed GIS analysis. Collaborating with the Weruweru Water Users Association (WUA), the project aimed to develop comprehensive maps of the catchment's hydrological features, including irrigation furrows and water abstraction points. Utilizing Android-based GPS devices, satellite imagery, and traditional surveying methods, field teams collected data on furrow dimensions and infrastructure conditions. GIS software facilitated the analysis, revealing critical issues such as blockages, leaks, and erosion. This approach not only improved the accuracy of water resource data but also empowered local communities by enhancing their capacity to manage and make informed decisions about their water resources. The project's success underscores the importance of community engagement and accurate data in developing equitable and sustainable water distribution policies. It serves as a replicable model for other sub-catchments facing similar challenges, highlighting the value of participatory mapping in environmental management.