Soil water infiltration evaluation from punctual to hillslope scales.

ABSTRACT

Quantifying infiltration and surface runoff at the hillslope scale is indispensable for soil conservation studies. However, the spatial and temporal variability of infiltration imposes a major constraint on surface runoff estimation. Point infiltration values do not fully express the complexity of the surface runoff in the landscape. Considering the need to improve the estimation of runoff volume from infiltration data, this study aimed to measure the apparent infiltration at hillslope-scale and compare it with two methods of infiltration estimative derived from point information. The study was carried out in six hydrological monitoring units paired. A set of hyetographs and hydrographs allowed the determination of apparent infiltration [Formula see text] to each monitoring unit as a function of precipitation rate P. The measured [Formula see text] values were used (1) to evaluate the efficiency of the different land management in increasing infiltration; and (2) to evaluate the efficiency of two methods of hillslope-scale infiltration estimation based on point data (a) derived from concentric rings method ([Formula see text]), and (b) derived from a physically-based modeling ([Formula see text]). Regarding the differences in land managements, terraces proved to be the most efficient land management practice, followed by phytomass addition. Regarding the methods, for precipitation rates greater than 40 [Formula see text] the point infiltration-based [Formula see text] underestimates apparent infiltration [Formula see text] with PBIAS ranging from [Formula see text] to [Formula see text]. Even so, [Formula see text] proved efficient in representing [Formula see text] at less intense rainfall events. Nonetheless, the point infiltration-based method [Formula see text] properly represented [Formula see text] to all rainfall intensities (Nash-Sutcliffe coefficient [Formula see text]).