Evaluation of eutrophic state of Alavian Dam Reservoir using statistical methods and TSI and TLI indices

Document Type : Research Paper

Author

Civil Engineering Department, Engineering Faculty, University of Maragheh, Maragheh, Iran

Abstract

Eutrophication is a global environmental problem that poses a serious risk to the conservation of dam lake water quality, human health and aquatic ecosystems. Indicators for determining the nutritional status of water bodies allow the decision to be made and the implementation of management strategies to control eutrophication. TSI and TLI indices and statistical analysis on phosphorus (TP), nitrogen (TN), chlorophyll.a (Chl.a) and Secchi depth (SD) parameters were used to assess the Eutrophic state of Alaviyan Dam Reservoir during 1394 to 1398. The results of parameter analysis showed that the values of total TSI and total TLI index for the lake in 1398 are 53.5 and 4.8, respectively, and thus the lake was placed in the eutrophic category. TN was the main cause of worsening water quality in spring, while in autumn TP had a greater share in the decline of water quality. In addition, the differences between the indices indicate that throughout the statistical period under analysis, phosphorus is not a factor that limits algal productivity and the mean value of 8.8 for the TN / TP ratio emphasizes that TN is the limiting factor of primary production. Studies have also shown that in addition to algae, which block light from passing to lower levels of the lake, non-algal turbidity can also affect the growth of phytoplankton. The parameters of total nitrogen, total phosphorus, and chlorophyll-a. have increased trend, which requires input nutrient controls into Alaviyan reservoir to preserve the water quality.

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