Water quality evaluation of the mainstream of Liaohe River based on fuzzy membership model

Scientific assessment of the river water quality spatiotemporal variation is of great significance for river water pollution prevention. In order to comprehensively measure the spatiotemporal changes of water quality in Tieling, Shenyang and Panjin sections of Liaohe River mainstream, an water quality integrated assessment indicator system was constructed. The thresholds and grading standards for each specific indicator and their integrated indexes were set based on the water quality monitoring data of three main national control sections in Liaohe River mainstream from 2012 to 2018. A fuzzy membership model was used to construct the comprehensive evaluation method of water quality. The results showed that the water quality of each monitoring section fluctuated at moderate and good levels according to the integrated assessment index, which varied between 0.5-0.7. In general, the downstream water quality was worse than the upstream water quality, and the water quality showed obvious regular changes with the seasonal changes. Some suggestions were put forward to realize the joint regulation and fine management of water resources and water environment in Liaohe River Basin. These included establishing a dynamic water use regulation mechanism based on water environment capacity in Liaohe River Basin as soon as possible, formulating a scheme of real-time relation between sewage discharge control and water quality monitoring, increasing the investment for water pollution control, and continuously improving the working mechanism of joint prevention and control of water pollution in the river basin.