It is of great significance to find a scientific way to assess the water quality of the middle route of the South-North Water Diversion Project. In this paper, the spatio-temporal changes of the 26 water quality indicators in 8 key monitoring stations along the middle route since the project was put into use were analyzed, and the modified Nemerow index method was employed to assess the water quality of the route in its early stage of operation. The results show that the water quality remained good in the period of study. Important water quality indicators were identified, including temperature, permanganate index, dissolved oxygen, total phosphorus, total nitrogen, mercury content, and density of planktonic algae. It is advised that potential ecological risks related to algae and shellfish reproduction in the open canal deserve special attention.


  • Analyzed the water quality of the MR-SNWTP since the operation.

  • Modified the Nemerow index method to evaluate the long-distance water conveyance project.

  • Compared the performance of the single factor method and the modified Nemerow index method.

  • Pointed out the water quality indicators that deserve special attention.

  • Put forward the suggestion of strengthening monitoring of potential risks posed by algae.

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