Dynamics of soil infiltrability of sloped lands under rainfall conditions measured with runoff-ponding method and the accuracy estimations

The soil infiltrability of sloped lands is of great importance to such studies and practices as hydrological process, soil erosion and water resources. The Runoff-Ponding Method is capable to the complete soil infiltrability process of sloped lands under rainfall conditions, which conceptually well represent the real processes of soil infiltrability and has not been possible with the traditional methods. In this study, the experimental data were used to illustrate the temporal functions of soil infiltration rates and cumulative infiltrations. The result indicated that the infiltration rates at slope locations well represented the transition of infiltration process from rainfall-controlled to infiltrability-controlled and eventually to steady infiltration stages. The cumulative infiltration volumes gradually reduced from the top to the lower slope locations, with lowered difference in infiltrated amount along the slope under faster runon advances on the surface. Theoretical analysis was made to determine the error in measured infiltration rate as affected by the error in measured distance of the runon advance. Wtaer balance was used to estimate the overall measurement accuracy. An analytical integration method was advanced to compute the cumulative infiltration which in turn was used to indirectly estimate the measurement accuracy of the method. The results indicate a very high accuracy of the method for infitrability measurement. This study will supply a reference basis for this method to be used in researches such as hydrology, soil erosion as well as water rsources.