Evaluation of global biogeochemical cycle in lotic and lentic waters by developing an advanced eco‐hydrologic and biogeochemical coupling model

Abstract

Recent research suggests reservoirs and dams have a great impact on the transformation of the carbon cycle in inland water. The author so far developed an advanced model coupling eco‐hydrology with biogeochemical cycle [National Integrated Catchment‐based Eco‐hydrology (NICE)‐BGC] and applied it to river basins to include the effect of global major reservoirs on biogeochemical cycles. In the present study, he extended NICE‐BGC to couple with LAKE2K in a stratified water quality model to evaluate the global biogeochemical cycle in lotic and lentic waters. Simulated water levels agreed with reasonably observed values there, which means that hydrologic budgets were simulated correctly. Simulated particulate organic carbon (POC) flux was relatively in good agreement with the author's previous study, whereas dissolved organic carbon (DOC) flux was not highly correlated. This result means that there are limits to the application of the same partial differential equations as in inorganic carbon for derivatives either with or without reservoirs as assumed by the author's previous study. Further, the result showed the difference in DOC flux has a positive relation and that of POC flux has a negative relation with nutrient concentrations. The simulated result also implies the amount of transformation from POC to DOC increases as the nutrient concentration increases in lentic water. Finally, the author evaluated changes in the global carbon cycle due to anthropogenic factors such as the construction of artificial dams with nutrient concentrations in lentic water. These findings provide valuable insights for re‐evaluation of carbon cycle change because the changes of fluxes in lentic waters rather depend not only on the difference in water level or discharge but also on retention time, nutrient conditions and water temperature.

Integrating ecohydrology and ecohydraulics

“…Similarly, the 3D hydrodynamic model when combined with a 2D groundwater and biogeochemical model have successfully determined the influence of bank slope angle and ambient groundwater discharge on biogeochemical reactive processes, such as aerobic respiration, nitrification and denitrification in the floodplain system. While the paper by Nakayama (2023) provides important insights into the reservoir's contribution to global carbon cycle, the paper by Liu et al (2023) unravels the denitrification zone at the interface between the main channel and the floodplain, where the hyporheic solute transport and biogeochemical activities would occur (Liu et al, 2023). Such interactive processes of ecohydrologic and ecohydraulic systems would greatly help maintain freshwater biodiversity and ecosystem function and generate ecosystem services.…”

“…An extended ecohydrologic model, NICE-BGC coupled with LAKE2K, has been found to be useful to evaluate the global biogeochemical cycling in both lotic and lentic waters. These models have successfully simulated particulate organic carbon (POC) and dissolved organic carbon (DOC) flux in hydropower dams (Nakayama, 2023). Similarly, the 3D hydrodynamic model when combined with a 2D groundwater and biogeochemical model have successfully determined the influence of bank slope angle and ambient groundwater discharge on biogeochemical reactive processes, such as aerobic respiration, nitrification and denitrification in the floodplain system.…”