对于美国西部的许多城市来说，住宅部门的室外用水构成了年需求的最大组成部分，文献中关于这一重要客户类别的实测灌溉效率的信息很少。掌握用水效率的准确信息对于规划节水计划非常重要。本文介绍了1188户住宅最终用水研究中测量的灌溉效率数据，该研究表明，这些住宅的景观平均使用了净蒸散量的50%。因此，任何针对这一群体的保护计划，如果假设它们通常过度灌溉，都将是徒劳的努力，实际上可能会产生增加用水的意外效果。 本文中的研究强调，成功的室外节水关键在于开发只针对那些具有最大节水潜力的客户的项目。负责管理城市用水需求的人员有责任获得准确信息，以确定任何节水计划的第一步目标是谁。本文描述了如何获得灌溉效率的准确信息，以及那些试图根据错误数据制定计划的人面临的陷阱。

For many cities in the western United States, outdoor water use in the residential sector makes up the single largest component of annual demand, There is little information available in the literature on measured irrigation efficiencies of this important customer category. Having accurate information on the efficiency of use is important for planning water conservation programs. This paper presents data on measured irrigation efficiencies at 1188 homes from the Residential End Uses of Water Study which demonstrates that these homes were applying an average of 50% of the net evapotranspiration to their landscapes. Consequently, any conservation programs aimed at this group with the assumption that they were generally over irrigating would represent wasted efforts, and might actually have the unintended effect of increasing water consumption. The research presented in this paper emphasizes that the key to successful outdoor water conservation lies in developing programs that are targeted only at those customers who offer the greatest potential for water savings. It is the responsibility of those charged with managing urban water demands to obtain accurate information on which to determine who to target as the first step in any water conservation program. This paper describes how accurate information on irrigation efficiencies can be obtained, and the pitfalls awaiting those who seek to base their plans on faulty data.