This paper presents the conceptual design of blue and green infrastructure (BGI) prototype focused on the decentralized stormwater collection, treatment, and storage in urban dwellings of semi-arid areas. The proposal emerges as an adaptation strategy to address water scarcity, taking into account the poor performance of conventional supply systems in such vulnerable contexts. The BGI system integrates two complementary strategies: direct collection from rooftops and collection of surface runoff generated on impervious sidewalks, which is conducted through permeable pavement to a bioretention cell composed of vegetation and recycled construction aggregates. This configuration allows runoff water to be collected, filtered, and stored for later use. Local climate data were used to estimate surface runoff, infiltration into the system layers, and potential storage in a preliminary water balance. The design was applied to a typical home with a roof area of 39.2 m² and a daily consumption of 724.9 liters (for five inhabitants, with water-saving devices). The results indicate that, during representative rainfall events, the volume captured partially covers this allocation for at least one day, demonstrating the hydraulic viability of the system in urban environments with limited space. It should be noted that the water balance did not consider losses due to evaporation or evapotranspiration, as the objective was to make a preliminary estimate for conceptual sizing. It is concluded that the BGI prototype represents a viable and sustainable alternative for harvesting rainwater in homes with limited space and access to conventional sources, thus contributing to the circular water economy.