Effects of Crop Growth on Hydrological Processes in River Basins and on Regional Climate in China

The regional climate model RegCM3 incorporating the crop model CERES, called the RegCM3_CERES model, was used to study the effects of crop growth and development on regional climate and hydrological processes over seven river basins in China. A 20-year numerical simulation showed that incorporating the crop growth and development processes improved the simulation of precipitation over the Haihe River Basin, Songhuajiang River Basin and Pearl River Basin. When compared with the RegCM3 control run, RegCM3_CERES reduced the negative biases of monthly mean temperature over most of the seven basins in summer, especially the Haihe River Basin and Huaihe River Basin. The simulated maximum monthly evapotranspiration for summer (JJA) was around 100 mm in the basins of the Yangtze, Haihe, Huaihe and Pearl Rivers. The seasonal and annual variations of water balance components (runoff, evapotranspiration and total precipitation) over all seven basins indicate that changes of evapotranspiration agree well with total precipitation. Compared to the RegCM3, RegCM3_CERES simulations indicate reduced local water recycling rate over most of the seven basins due to lower evapotranspiration and greater water flux into these basins and an increased precipitation in the Heihe River Basin and Yellow River Basin, but reduced precipitation in the other five basins. Furthermore, a lower summer leaf area index (1.20 m(2) m(-2)), greater root soil moisture (0.01 m(3) m(-3)), lower latent heat flux (1.34 W m(-2)), and greater sensible heat flux (2.04 W m())(-)(2) are simulated for the Yangtze River Basin.