Water footprint-informed spatial allocation of low impact development controls in a mixed-use tropical urban catchment in the Philippines

Flowchart showing the general methodology of the study, starting from water footprint accounting, water footprint assessment, and then LID allocation based on WFA results. Rapid urbanization and climate change are placing increasing pressure on urban water systems by exacerbating stormwater runoff, flooding, and water quality concerns. In response, low-impact development (LID) controls are increasingly being adopted as a sustainable approach to urban water management; however, their effectiveness depends strongly on strategic spatial allocation. This study applies water footprint accounting (WFA) as a data-driven approach for identifying priority areas for LID implementation in a mixed-use tropical urban catchment. A spreadsheet-based WFA tool was developed to automate the quantification of blue, green, and gray water footprints. The resulting water footprint estimates were mapped to identify hotspots representing critical pressure points within the catchment. Based on these hotspots, selected LID controls, including permeable pavements, rain barrels, and bioretention cells, were allocated and evaluated under varying rainfall percentiles. Simulation results showed that the proposed LID plan reduced runoff volume by up to 9.98% and peak runoff by up to 10.30% across subcatchments with LID controls implemented. These findings demonstrate the potential of integrating WFA with LID planning to improve urban hydrologic performance and support evidence-based stormwater management. Overall, the study highlights WFA as a useful decision-support approach for optimizing the spatial allocation of LID controls in mixed-use urban catchments, particularly in rapidly urbanizing tropical environments.