Abstract

GVOZDENOVICH, Jorge Jesus; BARBAGELATA, Pedro Anibal; OSZUST, José Daniel  and  PEREZ BIDEGAIN, Mario. Runoff and sediment production in a small agricultural watershed gauging of Entre Ríos, Argentina: application of the WEPP model. Cienc. suelo [online]. 2018, vol.36, n.1, pp.157-172. ISSN 1850-2067.

Soil erosion is a widely recognized problem. However, it is difficult to evaluate, reliably and accurately, the magnitude and rate of soil erosion at a field and watershed level. The Water Erosion Prediction Project (WEPP) is a continuous simulation tool, being capable of quantifying sediment and runoff processes at the field and watershed level. The objective of this study was to compare measured and simulated runoff in a watershed and estimate the sediment yield for different crop rotations using the WEPP model. The study was carried out in a small agricultural watershed of 27 ha, with Wheat/Soybean 2nd-Maize-Soybean crop rotation, near Paraná, Entre Ríos. Estimated soil losses from five crop rotations were compared: Continuous Soybean, Wheat/Soybean 2^nd, Continuous Maize, Maize-Soybean-Wheat/Soybean 2nd and Cover crop/Maize-Soybean-Wheat/Soybean 2^nd. Nash & Sutcliffe efficiency coefficient of index (E), regression analysis (R²), and analysis of variance were used for data analysis. Measured runoff water and WEPP simulated values were highly related (R² = 0.79), when analyzing 2012 and 2013 data set; with high variability in the total annual precipitated rain (1352.6 and 851.6 mm, respectively). Model efficiency was higher than the mean of the measured data (E = 0.66), which shows that, in the data set, WEPP was able to take into account climatic variability. Within the actual crop rotation, the agricultural watershed shows no observable signs of water erosion. Sediment yield simulated by WEPP was 4.8 Mg ha^-1 yr^-1, indicating an acceptable estimation. In the five crop rotations simulated, soybean monoculture presented the highest water runoff and soil loss. This may be because when higher volumes of water runoff are produced, water tends to concentrate on channels causing further interrill and rill erosion carrying higher amounts of sediments. The crop rotation that included cover crops reduced estimated runoff water and sediment production.

Keywords : watershed; water erosion; sediment; runoff.

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