No-tillage implementation: Analyzis on water-based sediment flow in the Marombas River, Brazil¹

Implantação da semeadura direta: Análise do fluxo de sedimentos na água do Rio Marombas, Brasil

HIGHLIGHTS:

The Soil Water Assessment Tools was suitable to represent the average daily flow and sediment flow in the Marombas watershed.

The hypothesis of reduced concentration of suspended solids (CSS) with increasing soil crop in the form of no-tillage system was accepted.

The alteration of the cultivation system along the watershed affected the CSS in the watershed outlet.

ABSTRACT

Water erosion is influenced by climate, soil, soil cover and soil conservation practices. These factors can be modified by natural (especially climate) and/or anthropogenic (especially soil, soil cover and conservation practices) actions. The relief factor also influences the water erosion and can also be partially modified by anthropic action. This study aimed to evaluate the impact of anthropogenic action due to the introduction of soil crop in no-tillage system on water erosion, and on the consequent flow of sediments in the water. The study was carried out in the Marombas river basin with an area of 3,939 km², using the Soil Water Assessment Tools (SWAT) model. The calibration and validation of the model for sediment production was carried out with a historical series of synthetic data. The data from this series were estimated by linear regression from sediment value load and the average daily flow obtained punctually in the basin’s outlet. The SWAT model was calibrated on a daily scale with data from 1979 to 1989 and was validated with data from 1994 and 1997. The SWAT model was suitable to represent the average daily flow and sediment flow in the Marombas watershed. The hypothesis of reduced sediment production with increasing soil crop in no-tillage system was accepted.

Key words:
soil conservation; erosion; hydrological modelling; Nash-Sutcliffe; SWAT model