According to the national criteria for flood forecasting in China (National Center of Hydrological Information (NCHI) 2000), the result of forecasting is qualificatory relative to peak value, total runoff volume, and peak time for this flood if the absolute percentage error of peak discharge and total runoff volume between the simulated and observed floods is less than 20%, and if the difference in peak time is within a routing period, respectively. The comparisons of three characteristics of the selected floods have been adopted to test the proposed algorithm. A typical flood in 2010 and a total of 27 historical floods with 3-hour routing periods between 2005 and 2010 are extracted for the study. Table 1 lists the initial ranges of Pa variable values and Table 2 shows the parameter values of the Xinanjiang model which are calibrated from historical flood data (Cheng et al. 2002, 2006; Wang et al. 2012).