Time scale analysis on the factors of hydrological process in Yuzixi catchment
渔子溪流域水文过程影响因素的特征时间尺度分析

Based on remote sensing images in three different years(1986,1994 and 2002),patch-dynamics model is used to simulate the annual land use/cover change(LUCC) from 1986 to 2004 in Yuzixi catchment.Using the modeling results of LUCC,the linear regression model and multivariate nonlinear regression model are employed to analyze the relationship between runoff,rainfall and LUCC at different time scales.The results show that:(1) The correlation coefficients between rainfall and runoff at different time scales are significantly different.The coefficient at monthly scale is the largest, which is 0.807.The coefficient at daily scale is the smallest(0.311).The results also show that,at daily scale,the time lag of rainfall and runoff has to be taken into account.(2) The results of partial correlation analysis show that,at different time scales,LUCC has significant impacts on the relationship between rainfall and runoff.At yearly scale,the impact of rainfall on runoff is larger than that of temperature on runoff,while the results at monthly scale are the reverse.The relationships between runoff and LUCC in Yuzixi catchment at different time scales are also different.Only at monthly scale,the significance of partial correlation analysis is acceptable.(3) At different time scales,the modeling accuracies of multivariate nonlinear regression analysis are higher than that of linear regression analysis.The nonlinear characteristics of different factors at different time scales are different.For example,the nonlinear index of rainfall at monthly scale is the largest(8.3) and the nonlinear index at daily scale is the smallest(0.4)(runoff is the dependent variable).The nonlinear index of temperature is 2.2 at month scale and the nonlinear index is 1.6 at daily scale.The nonlinear index of resident area is 0.725 at monthly scale and the nonlinear index is 1.01 at daily scale.