Seasonal Variation and Spatial Heterogeneity of Water Quality Parameters in Lake Chenghai in Southwestern China

Abstract

Seasonal dynamics and the vertical stratification of multiple parameters, including water temperature (WT), dissolved oxygen (DO), pH, and chlorophyll-a (Chl-a), were analyzed in Lake Chenghai, Northern Yunnan, based on monitoring data collected in 2015 (October), 2016 (March, May, July), 2017 (March, June, October), 2018 (August), and 2020 (June, November). The results indicate that the lake water was well mixed in winter and spring when the water quality was stable. However, when WT becomes stratified in summer and autumn, the Chl-a content and pH value changed substantially, along with the vertical movement of the thermocline. With rising temperature, the position of the stratified DO layer became higher than the thermocline, leading to a thickening of the water body with a low DO content. This process induced the release of nutrients from lake sediments and promoted eutrophication and cyanobacteria bloom. The thermal stratification structure had some influence on changes in DO, pH, and Chl-a, resulting in the obvious stratification of DO and pH. In summer, with an increase in temperature, thermal stratification was significant. DO and pH achieved peak values in the thermocline, and exhibited a decreasing trend from this peak, both upward and downward. The thermocline was anoxic and the pH value was low. Although Chl-a maintained a low level below the thermocline and was not high, there was a sudden increase in the surface layer, which should be urgently monitored to prevent large-scale algae reproduction and even local outbreaks in Lake Chenghai. Moreover, Lake Chenghai is deeper in the north and shallower in the south: this fact, together with the stronger wind–wave disturbance in the south, results in surface WT in the south being lower than that in the north year-round. This situation results in a gradual diminution of aquatic plants from north to south. Water quality in the lake’s southern extent is better than that in the north, exhibiting obvious spatial heterogeneity. It is recommended that lake water quality monitoring should be strengthened to more fully understand lake water quality and take steps to prevent further deterioration.

Seasonal Water Quality Changes and the Eutrophication of Lake Yilong in Southwest China

“…The trophic level index (TLI) method is used to evaluate and select representative algae that can reflect the reservoir comprehensive index of quantity evaluation of chlorophyll a as the dominant factor parameters, TN, TP and other four indicators are used as water eutrophication assessment basic factor of price. TLI has been widely used to assess the nutritional status of lakes, such as Lake Wuliangsuhai [7] and Lake Chenghai [8].…”

Comparative Study on the Determination of Chlorophyll-a in Lake Phytoplankton by a YSI Multi-Parameter Water Quality Meter and Laboratory Spectrophotometric Method

“…In eutrophic lakes, there was a significant positive correlation between Chl-a and TN, but there was no significant correlation between Chl-a and TN in mesotrophic and oligotrophic lakes. This indicated that phytoplankton growth was limited by TN and TP in eutrophic lakes, and TP was the limiting factor for phytoplankton growth in mesotrophic and oligotrophic lakes [32]. In the three trophic states of the lakes, there was a significant positive correlation between Chl-a and WT, DO and pH in both seasons and a significant negative correlation between Chl-a and depth.…”

Seasonal Variation of Water Quality of Taiping Lake in Eastern China

“…This method uses the covariance matrix of data to evaluate the strength of the relationship between two vectors. Normally, the Pearson's correlation coefficient between two variables, βi and βj, can be calculated as according to previous work [2]. Total phosphorus (TP) is the combination of various phosphorus species and is an important water quality parameter for investigating eutrophication of lakes and reservoirs [18].…”

“…Water quality indices are important references for measuring drinking water quality. However, numerous water quality indexes show seasonal fluctuation, which indicates the variation of water quality under different climatic conditions [2]. Currently, global warming is one of the major environmental problems that challenges the further development of human society [3][4][5].…”