Influência das características físicas do solo nas perdas de água por escoamento superficial no Sul do Brasil e Uruguai

Abstract

The objective of this work was to modeling runoff in soils with different physical characteristics, with three simulated rainfall intensities (30, 60 and 120 mm h-1) in Rio Grande do Sul and Uruguay. For simulated rainfall was used a portable rainfall simulator of multiple nozzles. Six plots were delimited by metal sheet borders (0,5 m2), with a runoff collector in the lower part. The runoff was determinate each five minutes. On each soil was determinate initial time and rate of runoff, rainfall (total, time and intensities), direction of slope, crop residue and cover percentage, soil densities (bulk and particle), soil porosity (bulk, macro and micro), textural fractions (clay, silt and sand), initial and saturated soil moisture. The runoff was estimated with Smith s modified model. The model parameters were adjusted by multivariate equations. The runoff losses accumulated in Uruguay was 64, 32, 30 e 15% from total rain, for Vertissolo 1, Chernossolo, Argissolo 2 e Vertissolo 2, respectively. The runoff losses accumulated in Rio Grande do Sul was 67, 45 and 27% from total rain, for Argissolo 1, Neossolo e Latossolo, respectively. In most of the cases, the initial runoff time decreased with increasing soil moisture and rain intensity, independently of the soil surface conditions. Smith s modified model estimated better the runoff with high soil moisture. The model adjustment was satisfactory for Rio Grande do Sul.