Comparison of the Effect of Equal Weights Parameters and Weighted Parameters by Use of Shannon Entropy Theory on Water Quality Index (Case Study: Fasa Plain)

One of the methods to determine the water quality is applying water quality index. This comprises several parameters with different effects on water quality. Therefore, one important problem is to calculate the exact value for each of the parameters. The purpose of the present study is to compare the effects of equal weights and weighted parameters on the results of water quality index in Fasa plain employing Entropy theory. To this end 9 Chemical parameters from 55 groundwater samples were investigated and ranked using the water quality index. Then, the weight of the parameters was calculated with the weights that obtained by the Shannon Entropy method. Thereafter, the significant difference was investigated between two groups. In order to determine the efficiency of each of these two methods, the Spearman's correlation was employed between the rating of wells quality in two methods and the rating of wells quality which was calculated by Sholer diagram. At the end, the clustering and qualitative zoning of wells were plotted. The results showed that there was a significant difference between the results of the water quality index whose weights obtained from the equal weights method and Shannon Entropy method in 0.01 level. Also, the high correlation (0.926) between ratings of wells quality by Sholer diagram method and ratings of wells quality was obtained by Shannon Entropy method indicates the high significance of this method in calculating water quality index.