U.S. Department of Agriculture: Forest Service -- National Agroforestry Center


Date of this Version



Written for presentation at the 2004 ASAE/CSAE Annual International Meeting. Sponsored by ASAE/CSAE. Fairmont Chateau Laurier, The Westin, Government Centre. Ottawa, Ontario, Canada. 1 - 4 August 2004.


Riparian buffers can improve surface water quality by filtering contaminants from runoff before they enter streams. Infiltration is an important process in riparian buffers. Computer models are often used to assess the performance of riparian buffers. Accurate prediction of infiltration by these models is dependent upon accurate estimates of infiltration parameters. Of particular interest here are Green-Ampt infiltration parameters, satiated hydraulic conductivity (Ko) and wetting front suction (hf). The objectives of this research were to (i) modify the Smith sorptivity procedure so that it can be used to estimate Green-Ampt infiltration parameters, (ii) Determine the relative closeness of Ko estimated by the inverse sorptivity and inverse Green-Ampt procedures and hf estimated by Rawls and Brakensiek (1985) to the laboratory-determined standards and (iii) Compare Ko estimates of the inverse sorptivity and inverse Green-Ampt procedures to those estimated by pedotransfer functions. This project was conducted at six sites in Nebraska, at which soil type and land use varied. The results of this study suggest that the inverse Green-Ampt procedure can be used to provide Ko estimates, even in the presence of macropores. Generally, pedotransfer function predictions did not estimate Ko well. Finally, hf as predicted by pedotransfer function was lower than laboratory-determined hf. These predicted infiltration parameters were used in the Green-Ampt infiltration equation to illustrate their effect on cumulative infiltration. Cumulative infiltration based on the inverse Green-Ampt procedure parameters resulted in the closest match to cumulative infiltration prediction from laboratory-based infiltration parameters at five of the six sites.