The main purpose of this study is to assess supply systems are well related to the chang of water quality and to discuss the efficiency of sampling method. Utilizing data from Shin-Sheng section of YEONG-HER survey, the assessment was made by sampling method and the analysis of variance. On the Whole, the conclusion of research are (1)average estimation of total dissovled solids are almost equal in three supply systems and sampling efficiency of stratification divided into directed and indirected system are good. (2)chlorine residual of indirected system are decreasing are sampling efficiency of stratification and stage are good. (3)PH value are lower in directed system than in indirected system and stratified sampling in not appropriate.
