Development of a global integrated modeling framework coupled with water quality module

The United Nations has proposed agendas for SDG published Agenda 2030, and its target 6.3, declares that water quality is still a global challenge. Approaching the water quality problem on global scale is deemed necessary. A large amount of past research on the representation of substance dynamics, such as biological activities and chemical changes of materials in water. However, due to the difficulties of integrating various models, assembling large datasets, and discrepancies in different regions, related studies focus on the global scale are not sufficient. In this study, a global spatially explicit hydrodynamic model with nutrient transport and biogeochemical processes with synchronous water temperature in the water bodies is fully coupled. They are also incorporated with the terrestrial process including land surface model, terrestrial nitrogen model, and additional nutrient datasets from previous studies. The phytoplankton is simulated on the global scale for the first time, and due to limited observations, the concentration of Chlorophyll-a is used for validating the integrated model. As result, the integrated model reproduced the yearly concentration of Chlorophyll-a in global rivers with reasonable accuracy. Additionally, the sensitivity of inorganic nutrient input was also tested in this study, and the values of different input and output are assessed. This new approach is useful for understanding and forecasting anthropogenic influence on ecosystems by introducing future input datasets to the land-water ecosystem by combining this spatially explicit, process-based biogeochemistry model in global surface water.