A time-varying distributed unit hydrograph method considering soil moisture

Abstract. The distributed unit hydrograph (DUH) method has been widely used for flow routing in a watershed because it adequately characterizes the underlying surface characteristics and varying rainfall intensity. Fundamental to calculation of DUH is velocity. However, currently velocity formula assumes global equilibrium ignores impact time-varying soil moisture content on velocity, which thus leads larger objective this study was identify factor, which, based tension water storage capacity curve, derived investigate response unsaturated areas. Thus, an improved hydrograph, content, obtained. proposed considered both intensity assuming be not but with moisture. Qin River basin Longhu were selected as two case studies, synthetic (SUH), (TDUH) current methods compared method. Then, influence evaluated, results showed that performed best among four methods. shape duration (UH) mainly related at initial stage rainstorm, when approximately saturated, grid dominated by excess rainfall. can watersheds sparse gauging stations limited observed runoff data.