Urban rooftop gardens in Lagos, Nigeria, face challenges in water management due to limited space and high population density. Smart irrigation schemes can help optimise water usage while enhancing garden productivity. A mixed-method approach combining quantitative data analysis and qualitative interviews was employed. A linear regression model (Y = β0 + β1X + ε) was used to estimate the impact of smart irrigation schemes on water usage efficiency. Smart irrigation systems in rooftop gardens reduced water consumption by an average of 25% compared to traditional methods, with a high level of confidence (95%) in these results. The methodology provided robust evidence for the efficacy of smart irrigation schemes in urban rooftop gardens, offering policy recommendations for sustainable water management policies. Policy makers should incentivize the adoption of smart irrigation systems to promote more efficient urban water usage and enhance garden productivity.