As a contribution to the GAME/HUBEX program, we used historical data and the Regional Climate System Model (RCSM) to analyze and simulate precipitation and streamflow in the Xixian basin. Historical data for the period 1982 to 1988 indicates that peak precipitation and streamflow occurs during the summer and early fall, when this region is affected by the East Asian summer monsoons and typhoons, respectively. In preparation for long-term coupled atmospheric and streamflow model simulations, we calibrated the RCSM’s semi-distributed hydrologic model (TOPMODEL) for the Xixian basin using observations from 1982 to 1984 and validated for the period 1985 to 1988 with good results.
Long-term hydroclimate simulations generated for the period January 1979 to December 1983 using the RCSM captured important hydroclimate characteristics of the region. The simulated seasonal precipitation and streamflow variations agree well with observations during late fall to spring. Summertime precipitation and streamflow were overestimated in the hindcast. The over-estimated precipitation may be due to the input large-scale forcing and the difficulty in simulating convertive precipitation during the monsoon season using a mesoscale atmospheric model. Coupled modeling of regional climate and streamflow is a relatively new capability. Implementation of this technique to river basins in the East Asia region will result in an increased predictability of water resources for this region.