Forecasting the quality of Nansi Lake water after the construction of the new channel of the Beijing-Hangzhou Grand Canal

The changes in the quality of Nansi Lake water due to the building of the new channel of the Beijing-Hangzhou Grand Canal are studied. The relationship between algae growth and environmental factors is analyzed. This relationship has practical significance and guiding value for Nansi Lake, it helps to prevent the outbreaks of water bloom effectively and ensure the stable development of economy, society and environment in the regions covered with the South-to-North Water Diversion Project. It is established that the use of the new channel of the Beijing-Hangzhou Grand Canal causes the following variations in the lake water: water temperature increases, while the values of pH, TP, and TN decrease. Besides, the content of Fe²⁺ in water depends on regional and seasonal peculiarities; the trend towards the stabilization of SiO₃ ² is observed. The new channel construction led to variations in chlorophyll-a content mainly due to changed water temperature and pH. Besides, riverbed digging and intense ship traffic also affect water characteristics.