Rainfall distribution in the Atlantic Rainforest

Abstract

Forest cover is of great importance in the context of water balance and may alter the mechanism of water absorption into the soil surface. The aim of this study was to evaluate the throughfall, stemflow, and surface runoff compared to rainfall in a fragment of the Atlantic Rainforest. Rainfall was measured through a rain gauge and a pluviograph installed on a tower above the forest canopy. To quantify the throughfall, six plots of 20 x20 m were laid, with 25 pluviometers five meters spaced from each other, for each plot. To measure the stemflow, collectors were adapted on the tree trunks having ≥ 15 cm circumference. For the runoff estimate, three plots were established with areas of 13.71 m², 14.79 m² and 14.86 m². The plots were demarcated with galvanized iron sheets. Based on the results, it can be concluded that forests play an important role in the hydrological cycle: from the total precipitation (1182.6 mm), one portion is intercepted by the tree canopy and evaporated back into the atmosphere; another portion (958.1 mm) corresponding to 81% of the total precipitation, passes through the canopy and hits the ground. The stemflow was 10.8 mm, corresponding to 0.9 % of the total rainfall. The runoff was 15.5 mm, which corresponds to 1.3% of the rainfall. The vegetation has an important role in reducing the runoff volume on the soil surface.