چكيده به لاتين
Sefidrood River and Al-Asi River are of the most important water resources in Iran and Syria. The two rivers have different usage like drinking, agriculture, industry and recreation. The water quality of these two valuable resources is negatively influenced by municipal and industrial wastewaters and agricultural drainages. For this reason, evaluation of their pollution intensity is required as a useful managing tool. Water Quality Index (WQI) is an easy way to check the water quality changes over time and place and to identify areas where have been threatened by pollution.
In the present work, five water quality indices in three categories (NSFWQIm and IRWQIsc for general uses, Smith and Oregan for recreation and Wilcox for agriculture) were calculated for Sefidrood and Al-Asi Rivers. For this purpose, the water quality parameters of both rivers were obtained from previous reports. The data of Sefidrood River belong to four seasons (from March 1391 to February 1392) and four stations (from the Sefidrood dam to the Tarik dam after Rostamabad). The data of Al-Asi River belong to four seasons in year 1388 and two stations including Alameiri and Rable. After calculating the Water Quality Indices, the Giljanovic comparison method was used to compare the selected indices in terms of their performance in water quality evaluation. Then, to found the causes of superiority of one index to another one, the Shannon entropy analysis was performed.
By comparing the obtained amounts of indices for the two rivers, it was found that the water quality of Al-Asi River was more suitable than that of Sefidrood River for general uses, recreation and agriculture. According to both NSFWQIm and IRWQIsc indices, the best water quality of Sefidrood River at the two of the stations was in spring and winter and at the two others was in spring and summer. The worst quality was in autumn at all stations according to the both indices. In addition, on the basis of NSFWQIm, the water quality of Al-Asi River was more appropriate in winter and spring. However, according to IRWQIsc the best and the worst water quality were attributed to autumn and spring, respectively, for this river.
Comparison of the WQIs using Giljanovic method indicated that the NSFWQIm and Smith were the most suitable indices for monitoring Sefidrood River for general and recreational uses, respectively. Besides, IRWQIsc and Smith were distinguished as the most appropriate indices for monitoring Al-Asi River for the aforesaid uses.
Entropy analysis was used to identify which parameters were responsible for the water quality changes and made a specific index superior than the others. The results showed that the most effective parameters on Sefidrood River quality were turbidity, phosphate and fecal coliform. On the other hand, it was found that NSFWQIm and Smith indices were more appropriate for evaluation of Sefidrud River quality for general and recreational uses, respectively. This was due to the larger relative weight of fecal coliform in the NSFWQIm index (0.16) than that in the IRWQIsc index (0.02). But for the two parameters of phosphate and turbidity, the relative weights did not differ much for the two indices (0.08 and 0.09 for turbidity and 0.10 and 0.13 for phosphate in NSFWQIm and IRWQIsc, respectively).
From the three of the parameters that affecting the quality of water in Sefidrud River, fecal coliform and turbidity are present in Smith, fecal coliform and phosphate are present in Oregon Index. According to Shannon's entropy analysis, among the aforesaid most effective parameters on the water quality of Sefidrud River, turbidity had the smallest amount of entropy corresponding to the biggest variation rang. Therefore, since turbidity does not exist in the Oregon index, its variations did not influence on the amount of Oregon index. In contrast, the Smith's value was controlled by turbidity since it often varied in an inappropriate range.
The most effective parameters in Al-Asi River were phosphate, nitrate and turbidity according to Entropy analysis. From the three parameters mentioned above, turbidity and phosphate in the IRWQIsc index have a higher relative weight compared with the NSFWQIm index. This has resulted in a better performance of IRWQIsc than NSFWQIm in describing the water quality of the Al-Asi River.
In addition, comparison of Smith and Oregan indices using Giljanovic method indicated that the performance of the two indices was not significantly different. Among the aforesaid effective parameters on the water quality of Al-Asi River, turbidity exists in the Smith index and Phosphateis exists in the Oregon index. In general, the Oregon index expressed better the good water quality and the Smith index described better the average and bad quality.
Keywords: Sefidrood river, Al-Asi river, Water Quality index, Giljanovic comparison method, Shannon entropy analysis
