CGER Reports


Development of Process-based NICE Model and Simulation of Ecosystem Dynamics in the Catchment of East Asia (Part II)

Tadanobu Nakayama [Asian Environment Research Group, National Institute for Environmental Studies (NIES)]

Human activity has dramatically changed the ecosystem dynamics of East Asian catchments. Conservation of the global environment and realization of a society in harmony with nature have recently become important challenges. To facilitate sustainable development, it is necessary to quantify the mechanisms of ecosystem change and to perform restoration work that will actively recover local natural environments that have been damaged in the past. Numerical models in combination with observation and satellite data are very powerful tools in this river-basin-wide process (Fig.1).

Fig.1 Combination of grid-based models, observations, and satellite data.

This monograph (Part II) is the successor to the 11th publication (Part I), which appeared in 2006. The catchments described here are representative of areas in Japan where human activity has greatly affected the environment. In Japan, regulations promoting nature restoration took effect on January 1, 2005. They include various measures to promote symbiotic relationships between humans and ecosystems. The development of the NIES Integrated Catchment-based Eco-hydrology (NICE) model (Fig.2) and the simulation of ecosystem dynamics in these catchments are very important for the quantitative evaluation of catchments.

Fig.2 Process-based NICE (NIES Integrated Catchment-based Ecohydrology) model. NICE simulates the water-heat budget, mass transport, and vegetation succession processes iteratively.

In this monograph (Part II), the author reviews examples of the model application to the catchments where new Nature Restoration and Urban Area Regeneration Projects have been started. For example, the author introduces results from the contribution of groundwater seepage to eutrophication in Lake Kasumigaura (Fig.3), prediction of groundwater level changes in the Kanto Plain (Fig.4), and reproduction of alder invasion in the Kushiro Mire (Fig.5).

Fig.3 Distribution of annual-averaged (a) interpolated groundwater nitrogen concentration, (b) simulated groundwater seepage, and (c) simulated total inflowing nitrogen loading in Lake Kasumigaura. The simulation showed that high nitrogen load in groundwater seepage, despite government policies to prevent overland flow of nutrients into the lake, plays an important role in eutrophication of the lake.
Fig.4 Predicted groundwater level changes at the ecosystem service (ES) sites for four scenarios in the Kanto Plain: (a) block renewal by detached houses, (b) block renewal by collective housing, (c) farmland and productive green areas, and (d) parks and open space. The simulated results indicate that underground urban structures in the Tokyo metropolitan area have a great impact on hydrologic changes in the catchment.
Fig.5 Simulated spatial distribution of alder invasion up to the present in the Kushiro Mire. NICE reproduces this invasion excellently, and represents a dramatic advance in our understanding of the associated drying phenomenon.

NICE is being further developed to evaluate water-heat-mass dynamics in relation to human activity in East Asia. The author plans to report this research in another monograph (Part III) in the near future.