The multiplier effect and systemic patterns of urban reclaimed water utilization

Abstract

The multiplier effect describes how an initial change in a variable leads to a larger overall impact through interconnected processes. The utilization of reclaimed water offers a promising solution to water scarcity while preserving fresh water for diverse applications. Integrating reclaimed water into urban water systems alters both the balance and composition of water resources and affects system efficiency. However, there is currently no unified method for evaluating the efficiency of reclaimed water utilization (RWU). This paper introduces the concept of the multiplier effect to establish a comprehensive evaluation framework. The mechanism of the multiplier effect is dissected, an accounting methodology for the reclaimed water utilization multiplier (RWUM) developed. We also further identify various RWU patterns and their impacts on the multiplier estimation. By examining case studies in Singapore and Chongqing, the paper explores how to increase the RWUM with the multiplier accounting. We found that the multiplier effect enhances the optimal utilization of available water resources, thereby improving both the effectiveness and efficiency of urban water systems. Improving each component's performance increases RWUM and boosts overall water system efficiency. Selecting an appropriate systemic pattern significantly enhances the efficiency of reclaimed water use. Increasing reclaimed water use rates, refining its application patterns, and improving urban water cycle operations significantly boost RWU efficiency and urban water system performance. The methodology for RWUM evaluation provides a comprehensive and standardized framework for assessing the utilization efficiency of urban reclaimed water, yielding comparable results. This framework can guide the planning and management of urban reclaimed water systems and is applicable to various global water systems for cities alike.