Rainwater harvesting systems as a sustainable water management strategy: addressing water security challenges in Sri Lankan buildings

Abstract

Water scarcity has emerged as a critical challenge with wide-ranging implications for economic development, public health, and ecological balance. Despite receiving approximately 2,000 mm of annual rainfall, Sri Lanka struggles with inefficient rainwater capture, resulting in significant runoff losses and growing urban water stress. While rainwater harvesting systems (RWHS) have been recognized for their sustainability potential, existing studies rarely examine the critical gap between policy mandates and their practical implementation in urban buildings. This paper addresses this gap by critically evaluating RWHS as a decentralized water management strategy for Sri Lankan buildings, with a focus on bridging policy–practice disconnects. Drawing on empirical evidence, policy documents, and comparative global practices, the study analyzes RWHS design elements, treatment technologies, performance indicators, and institutional frameworks. Case studies demonstrate that well-designed RWHS can reduce reliance on conventional water supplies by over 70% in institutional and commercial settings, while also contributing to stormwater management and climate resilience. However, widespread adoption remains constrained by inconsistent enforcement, limited incentives, and insufficient public awareness. This paper offers context-specific recommendations for integrating RWHS into urban planning and building codes more effectively. By clarifying these implementation barriers and solutions, the study contributes new insights that can guide policymakers, urban planners, and building professionals to leverage RWHS as a transformative tool for achieving Sustainable Development Goal 6 and long-term water security in Sri Lanka.