Abstract:This study aims at monitoring the behaviour of the rainfall, runoff, drainage, soil water storage, and evapotranspiration variables involved in the water balance measured by lysimeter data. The evaluation of the water balance considered different time scales, where the components were monitored daily and in 10-day accumulated period intervals. The results demonstrated that in wet periods the soil water content was greater at a depth of 10 cm, whereas in the dry periods a greater concentration was observed at 70 cm depth. At the depth of 30 cm, the lowest values of soil water content were observed for both wet and dry periods. The results, obtained through the use of tensiometers and time domain reflectometry installed internally and externally to the lysimeter, were very close, which was more noticeable during the periods of lower water loss by the soil. The water balance, calculated from the lysimeter data, demonstrated that 70% of the total rainfall was lost by the process of evapotranspiration. The drainage accounted for 27Ð5% of the precipitated water, highlighting the fact that this component should not be disregarded in the water balance calculation.

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The objetive of this work was monitoring of the soil water content behavior, for grass native field and native forest vegetation cover, in an area characteristic of Atlantic Forest in Southern Brazil. To obtain the soil water content, some electronics tensiometers with pressure transducer were utilized and were placed 0.10, 0.30 and 0.70 m below the soil surface, from October 2010 to May 2011. The values of matric potential, measured by tensiometers, were transformed into soil water content values based on a soil water retention curve for each depth. The obtained results showed that in native fields and native forests, the greatest variations of tension, water content, and water storage in the soil happened at a depth of 0.10 and 0.30 m. At a depth of 0.70 m these variables presented less variations, mainly in native field soil cover. The soil water content was greater in the forested land cover than in the native field. Different seasons throughout the year directly influenced the behavior of analyzed variables. In the summer, the values of soil water tension observed in the forested land cover were higher than those observed in the native field. In the winter season, there was a change in that behavior at depths of 0.30 and 0.70 m and the values of soil water tension became smaller than the forested land cover. Great variations in the soil water tension were observed from October to April (summer), and became steady after May (in the beginning of winter). In the grass native field, most of the time, the greatest soil water content was observed at a depth of 0.10 m followed by depths of 0.70 and 0.30 m, respectively. During dry periods, the greatest soil water content was observed at a depth of 0.70 m, followed by depths of 0.10 and 0.30 m, respectively. In the forest, except for rainy periods, the greatest content of the soil water occurred at a depth of 0.70 m. For the conditions of this study, the total storage of water in the soil was 31.05% greater in the native forest than in the native field.