Oxygen dynamics in large reservoirs: A new framework for understanding the formation of metalimnetic oxygen minima

• Applicants: Professor Johannes Barth, Ph.D.; Dr. Karsten Rinke
• Subject Area: Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 410560381

Dissolved oxygen (DO) is a key quantity in water quality management of lakes and reservoirs. It is essential for the ecosystem functioning of these lentic ecosystems. Too low concentrations (anoxia) limit the usability of water for drinking and other purposes. Additional health issues arise from anoxic waters. Last and not least, water treatment becomes expensive. Hence, a healthy and sustainable operation of our freshwater bodies is of prime public interest. Therefore, we propose cooperation between scientists of a leading Chinese and German research institutions involved in water research with a reputation for approaching novel and challenging environmental concerns inside and outside their own countries. Both, numerical simulation tools as well as field experiments & measurements will be operated at the forefront of currently available equipment. From this collaboration, we anticipate a mutual understanding for existing water issues, an intensive exchange about modern field equipment and the implementation of such data in numerical simulations and finally more sensibility of how new knowledge about water issues and reservoir management are put into practice in the other country. Water is a central health issue and the public profits from improved water quality. Oxygen reacts highly sensitive against environmental stressors like organic pollution, eutrophication or climate change. The prediction of its dynamics is a challenging task due to the complex interaction of ecological, biogeochemical, and physical processes. While the dynamics of hypolimnetic DO have been studied intensively and, as a consequence, can be predicted with sufficient accuracy for many purposes, the dynamics of DO in the metalimnion (i.e. the layer between the warm upper epilimnion and the cold, deep hypolimnion) have been understood far less. Metalimnetic oxygen minima (MOM), a phenomenon known from freshwater and marine systems, arise from a combination of high oxygen demand and low vertical exchange. The causal factors of the increased DO demand within the metalimnion are subjected to speculation and involve alternative mechanisms like plankton respiration, imported allochthonous material, turbidity-bound respiration or the breakdown of sedimenting material. The aim of this proposal is the implementation of high-resolution DO-monitoring in German and Chinese Reservoirs (Rappbode Reservoir and Panjiakou Reservoir) together with field and laboratory experiments for testing various hypotheses about the drivers of DO consumption. Results of the field and lab experiments as well as high-resolution monitoring studies are conceptualized by mathematical process descriptions that are embedded in 1D and 3D coupled hydrodynamic-biogeochemical lake models. The developed model tools are provided to the scientific community in model frameworks based on open source codes.

• DFG Programme: Research Grants
• International Connection: China
• Partner Organisation: National Natural Science Foundation of China
• Cooperation Partners: Professor Dr. Suiliang Huang; Professor Dr. Wenqi Peng