中文摘要：

分析了灌区节水和非点源污染存在尺度效应的原因和机理，针对田间尺度不能代替灌区尺度、而灌区尺度又过于复杂的特点，提出灌区小流域的尺度概念。灌区小流域既是灌区流域的基本生态结构单元，又是田块这一更小尺度的集合体。论述以灌区小流域为单元进行节水和非点源污染管理的可行性和必要性，并对灌区小流域节水和非点源污染管理的研究内容和研究方法提出参考意见。

英文摘要：

Mechanisms of scale effect on water saving irrigation and non-point source pollution were analyzed. Because of scale effect, field scale can＇t be used as a substitute for irrigation system scale, and irrigation system scale was too complex for study, therefore, the concept of small watershed of irrigation system （SWIS） was defined. Being the basal ecology unit of irrigation system, SWIS was also an aggregation of a number of fields, a much smaller scale unit. Feasibility and significance of water saving irrigation and non-point source pollution management in SWIS were demonstrated, and then comments and opinions were brought forth on contents and methods of studies on water saving irrigation and non-point source pollution management in SWIS.