North China Plain (NCP) is one of the most important grain cropping areas in China. Furthermore, there are some megalopolis, such as Beijing and Tianjin. This region has changed from water-rich in the 1950’s to water-poor area at present, which indicates various ecosystem degradations such as dry-out Yellow River, nearly closed Hai River, groundwater degradation and seawater intrusion in the NCP. The author has so far developed the process-based model, called NIES Integrated Catchment-based Eco-hydrology (NICE) model (Nakayama, 2008; Nakayama & Watanabe, 2004, 2006, 2007; Nakayama et al., 2006, 2007), which includes surface-unsaturated–saturated water processes and assimilates land-surface processes describing the variation in phenology with satellite data. This model was applied to the Hai River and the lower reach of Yellow River in order to evaluate water/heat dynamics in agricultural and urban areas, and their relation to crop productivity.

Results/Conclusions  

The model reproduced excellently river discharge, groundwater level, evapotranspiration, and crop productivity of summer maize and winter wheat. It reproduced excellently the trend of groundwater degradation over the previous half century, including cone depressions occurred around the bigger cities, which the previous research (Nakayama et al., 2006) could not reproduce. The simulation also clarified that this water shortage is related to little flow discharge to the ocean in the Hai River. Furthermore, the simulated result of density current and solute transport processes made clear that these water cycle changes have caused the serious seawater intrusion and the decrease of crop productivity beside the coastal area, which could be shown in NDVI (Normalized Difference Vegetation Index) value estimated by the satellite images. The model reproduced well this degradation of crop productivity around the coastal area by adding newly the deficit factor by irrigation water salinity to the NICE model, which shows that this model is very powerful to simulate the future crop productivity in relation to the water withdrawal in this area.

References;

Nakayama, ECOMOD, doi: 10.1016/j.ecolmodel.2008.02.017, 2008 (in press).

Nakayama & Watanabe, WRR, doi: 10.1029/2004WR003174, 2004.

Nakayama & Watanabe, HESSD, 3, 2101-2144, 2006.

Nakayama & Watanabe, HP, doi: 10.1002/hyp.6684, 2007.

Nakayama, et al., HP, doi: 10.1002/hyp.6142, 2006.

Nakayama, et al., STOTEN, doi: 10.1016/j.scitotenv.2006.11.033, 2007.