Water shortages are one of the most crucial treats to sustainable development of society. Reclaimed water is considered as a safe, reliable and sustainable water source to satisfy water demands in many water-scarce areas. This International Standard is intended to standardize the benefit evaluation of reclaimed water use, guiding the progress of planning, designing, operating, management and evaluation of water reuse benefits. This International Standard is applicable to practitioners and regulatory authorities who propose to implement principles and guidelines on evaluation of reclaimed water use benefit, which aims to achieve a reasonable and comprehensive evaluation of reclaimed water use, identify the key benefits of reclaimed water use at local and regional levels, further expand water reuse market and improve water reuse efficiency. This International Standard presents: - Standard terms and definitions; - Evaluation indicators of reclaimed water use benefit, including resource benefit index, environmental benefit index, social benefit index, economic benefit index, etc; - Procedures of benefit evaluation of reclaimed water use; - Evaluation indexes with respect to different aspects of reclaimed water use benefit.