这里描述的是一个系统模型，用于对具有饮用水、亚饮用水和非饮用水水源以及双重或多重配水系统的城市供水系统进行技术和经济分析。双重供水的好处有两个:一是可以消除多年内持续摄入低水平有毒污染物对健康造成危害的风险，二是可以将原本用于不保证高质量水的可转售或不可转售用途的优质水保存起来，供饮用。包括3个参考文献、图表。

Described here is a systems model for technical and economic analysis of an urban water system having potable, subpotable, and nonpotable sources and dual or multiple distribution systems. The benefits of dual water supply are twofold: the risk of a health hazard from continuous ingestion of low levels of toxic contaminants over a period of years would be eliminated, and the good quality water, which otherwise would have been used for subpotable or nonpotable purposes not warranting high quality water, would be conserved for potable use. Includes 3 references, figures.