Abstract
Water quality degradation is one of the major problems with artificial lakes in estuaries. Long-term spatiotemporal patterns of water quality in a South Korean estuarine reservoir were analyzed using seasonal datasets from 2002 to 2020, and some functional changes in relations of trophic state variables due to the construction of serial weirs in the upper river were also investigated. A total of 19 water quality parameters were used for the study, including indicators of organic matter, nutrients, suspended solids, water clarity, and fecal pollution. In addition, chlorophyll-a (CHL-a) was used to assess algal biomass. An empirical regression model, trophic state index deviation (TSID), and principal component analysis (PCA) were applied. Longitudinal fluctuations in nutrients, organic matter, sestonic CHL-a, and suspended solids were found along the axis of the riverine (Rz), transition (Tz), and lacustrine zones (Lz). The degradation of water quality was seasonally caused by resuspension of sediments, monsoon input due to rainfall inflow, and intensity of Asian monsoon, and was also related to intensive anthropic activities within the catchment. The empirical model and PCA showed that light availability was directly controlled by non-algal turbidity, which was a more important regulator of CHL-a than total nitrogen (TN) and total phosphorus (TP). The TSID supported our hypothesis on the non-algal turbidity. We also found that the construction of serial upper weirs influenced nutrient regime, TSS, CHL-a level, and trophic state in the estuarine reservoir, resulting in lower TP and TN but high CHL-a and high TN/TP ratios. The proportions of both dissolved color clay particles and blue-green algae in the TSID additionally increased. Overall, the long-term patterns of nutrients, suspended solids, and algal biomass changed due to seasonal runoff, turnover time, and reservoir zones along with anthropic impacts of the upper weir constructions, resulting in changes in trophic state variables and their mutual relations in the estuarine reservoir.
Highlights
Water quality plays an important role in providing sustainability for human use and ecological balance within reservoirs [1]
Our study showed that seasonal and spatial variations in water quality in the system are typically regulated by the hydroclimatic regime and longitudinal zonation and that the variations were altered by the construction of serial upper weirs
These were linked with intensive human activities within the catchment, which resulted in high levels of inorganic and organic matter, fecal coliform bacteria, and suspended solids during summer and autumn
Summary
Water quality plays an important role in providing sustainability for human use and ecological balance within reservoirs [1]. Public Health 2021, 18, 12568 some dams are constructed in this transition region to provide a number of socio-economic benefits such as flood control, irrigation water, hydroelectric generation, storm surge mitigation, and permanent freshwater source [7] They meet the needs of the people, there are water quality problems in estuarine systems related to the dams. Chlorophyll-a (CHL-a) is the main indicator of algal biomass in aquatic environments and is one of the most important parameters for assessing eutrophication in reservoirs, as it is closely related to various environmental factors [20]. The estuarine reservoir is still facing continuous and seasonal water quality problems such as oxygen depletion [15,34], high rate of sedimentation, increased anthropogenic discharges (organic matters and nutrients), and eutrophication [15,35,36,37]. The second objective was to investigate the impact of the construction of serial headwater weirs on the trophic state variables and their functional relations in the estuarine reservoir
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
