Correlation analysis between low-flow recession coefficient and surface landform characteristics in karst basin

In light of the storage and adjustment for runoff by topography and landform features in dry season, daily observed flow data during dry seasons from19 hydrology stations located up the Sinan station of the Wujiang River are analyzed to find out base flow recession law. According to the characteristics of low flow recession curve, the base flow is divided into two parts, fast fissure flow and slow fissure flow, and the corresponding recession coefficient is calculated. Based on the single factor and multi-factor regression analysis between the recession coefficient and the basin's landform features, elevation eigenvalue and topographic index eigenvalue are determined as the main factors affecting the recession coefficient. The dual non-linear regression equations are established with these two eigenvalues and the recession coefficient(a1=0.781-0.266?ln(x)+0.633?ln(y)and a2=0.061-0.016?ln(x)+0.044?ln(y)),their confidence intervals are greater than99%,so these two curves fit significantly and these equations can be used to regionalize the recession coefficients and to provide the basis for hydrological simulation in ungauged basins.