Researchers led by Prof. CHEN Yushun from Institute of Hydrobiology (IHB) of the Chinese Academy of Sciences found that water transfer system in the Eastern Route of South-to-North Water Diversion Project (ER-SNWDP) improved water quality in the northern lakes along the route by providing sufficient water and accelerating water circulations.

The study was published in Water Research on August 6.

Using both multiple statistical methods and the Water Quality Index (WQI) model, the researchers conducted a holistic assessment of water quality condition and spatiotemporal patterns in impounded lakes along the ER-SNWDP.

These series of lakes included Gaoyou Lake, Hongze Lake, Luoma Lake, Nansi Lake, Dongping Lake and Donghu Lake, all of which are shallow lakes and provide multiple benefits and important ecosystem services.

The WQI indicated an overall "Good" water quality with an improving trend from southern to northern lakes.

The southern Gaoyou Lake and Hongze Lake showed relatively higher nutrients, turbidity, and total suspended solids. The northern Dongping Lake and Donghu Lake showed higher conductivity, total hardness, and chloride, and the Luoma Lake and Nansi Lake were intermediate between the two former groups.

China's South-to-North Water Diversion Project was launched in 2002 to divert freshwater from the Yangtze River basin to Northern China Plain for addressing water shortage and improving water quality. The key issue of the ER-SNWDP is water quality.

The open water transfer system in the ER-SNWDP is easier susceptible to point sources pollution from urban sewage and industrial waste water, and non-point sources pollution from agriculture, soil erosions, and others.

This study improved the understanding of the spatiotemporal water quality patterns of the impounded lakes in ER-SNWDP, and can be used to develop water quality management strategies.

Nevertheless, it remains to concern that diffusion of pollutants from surrounding watersheds could be accelerated by water transfer at a certain extent, which may increase potential risks of water pollution in the water receiving area.

 Aquatic macrophyte in Dongping Lake (Image by IHB)