Abstract
Due to rapid increases in socioeconomic development and the human population over the past few decades, the shallow lakes in China have suffered from eutrophication and poor water quality. The conditions in Lake Dianchi Caohai, which is in the northern part of Lake Dianchi, are considered the most serious. The ecological restoration of Lake Dianchi Caohai began in the late 1980s. Lake managers and the public have been puzzled by the lack of a significant response of the water quality to the flow pattern despite the tremendous investment in water quality improvements. Therefore, lake managers desperately need to understand the responses of pollutant behaviors to proposed management measures. In this paper, a depth-averaged two-dimensional hydrodynamic and water quality model based on hydrological data, measured lake bed elevation, and water quality data is developed to simulate the flow field and water quality of Lake Dianchi Caohai. This model was validated using water quality data from the Caohaizhongxin site in 2016, and a close agreement was found between the model results and observations. Wind-driven circulation in Lake Dianchi Caohai was observed in the model results, which revealed that the lake flow pattern was dominated by wind-driven circulation, while the inflow/outflow played only a subsidiary role during this period. The formation of the wind-driven current in Lake Dianchi Caohai could be roughly divided into three stages. The hydrodynamic processes connected with the distribution of chlorophyll a are evaluated and discussed to adequately understand the hydraulic mechanisms driving the accumulation of cyanobacteria. Moreover, we designed three scenarios after comparing all possible operation scenarios to analyze the contributions of each different operation scenario to the water quality improvements. The optimal ecological operation scenario which has the best impacts on the water quality, especially the reduction in Chla and NH3-N concentration, is proposed based on our comprehensive analysis. The water quality improvement and management suggestions proposed in this paper are based on lake flow patterns and make up for previous studies that did not consider the effects of hydraulic characteristics on water quality improvement in Lake Dianchi Caohai.
Highlights
Shallow lakes, which provide nutrients and habitats for aquatic animals and freshwater and food for humans, are distributed in densely populated areas with low-lying terrain in China [1,2,3,4].Substantial changes to ecosystem functions are occurring in many shallow lakes, such as the decrease in water area, the degeneration of aquatic ecology, the proliferation of cyanobacterial blooms, and the reduction in drinking water supplies due to severe water quality problems, which have all occurred in Dianchi, Taihu, and Chaohu lakes [5,6,7,8,9]
The water quality improvement and management suggestions proposed in this paper are based on lake flow patterns and make up for previous studies that did not consider the effects of hydraulic characteristics on water quality improvement in Lake Dianchi Caohai
Climate changes accompanied by rising air temperatures and changes in wind speed and direction can indirectly affect the water temperature structures of lakes and change the hydrodynamic conditions in shallow lakes to accelerate the occurrence of water pollution and toxic cyanobacterial blooms, which are the key characteristics of eutrophication [3,10,14,15]
Summary
Shallow lakes, which provide nutrients and habitats for aquatic animals and freshwater and food for humans, are distributed in densely populated areas with low-lying terrain in China [1,2,3,4]. The freshwater was polluted, and cyanobacteria were enriched in the eastern part of Lake Dianchi Caohai and the northern part of Lake Dianchi Waihai under the effects of adverse water flow conditions in August [34] To overcome this problem, the utilization of advantageous hydrodynamic conditions may be a valuable strategy to improve the water environment because such conditions can improve the water replacement efficiency, decrease chlorophyll a (Chla), which is an indicator of phytoplankton biomass and pollutants, and even change essential hydraulic conditions, which are crucial in accelerating eutrophication. The influences of meteorological conditions and water quality factors on Chla concentration that indicates phytoplankton biomass in Lake Dianchi Caohai were analyzed by Wei [8], and their results showed that TP might be the most important factor for the control of phytoplankton biomass Despite their importance, these previous studies, which focused on only water quality trends and bioremoval efficiency, neglected water flow-field dynamics. Based on the results from this study, optimal ecological operations and suggestions for lake restoration are proposed
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
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 callMore From: International Journal of Environmental Research and Public Health
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
