ABSTRACT: Little is known about the groundwater recharge potential of weathered tropical catchments, where increasing water uptake is widespread to meet various water demands. This study aimed to estimate the volume of groundwater recharge of the Doce River Basin, Minas Gerais, Brazil. The BALSEQ model was applied to calculate the water balance over a period of two years (2007-2009). Evapotranspiration, runoff, and potential groundwater recharge (PGR) were calculated, using daily data on rainfall, potential evapotranspiration, and plant-available water. A soil survey was undertaken for all major soils occurring in the basin. Soils samples were used to determine hydraulic conductivity, bulk density, and water content at field capacity and at the permanent wilting point. Vegetation data were obtained from the literature and used to determine the following parameters: canopy interception, crop coefficient, and root depth. The estimated groundwater was spatially predicted using the Random Forests model with digital elevation, vegetation index, pedological, lithological, and climate maps. During the two years, an average of 32 % of rainfall was converted to groundwater. Annually, the percent of rainwater converted to groundwater varied between 27 and 48 % for all soil classes, highlighting the great temporal variability. The spatial prediction showed a volume of approximately 17,484 and 35,410 m3 of rainfall being converted to groundwater for the first and second year, respectively. The BALSEQ model showed a feasibility for the water balance calculation and can be reapplied for updating the groundwater maps of the Doce River Basin. These maps could then be used to guide land use planning programs, with the aim to protect water resources.

This study aimed to relate changes in structure and species diversity with edaphic variables (soil type and flooding regime) in a gradient of forest formations within the Brazilian restingas (coastal woodlands). The study was carried out in the Jacarenema Municipal Natural Park, in the city of Vila Velha, in the Espírito Santo State, Brazil. We evaluated the structure of shrub and tree components by sampling 80 plots of 5 × 25 m each, equally distributed among four forest types (well-drained, transitional, floodplain and flooded). We included all individuals with a ≥ 3.2 cm diameter at breast height. From each plot, soil samples (for chemical and physical analysis) were collected at a depth of 0-10 cm. We identified a significant fertility gradient (of soil nutrient availability) and a strong influence of groundwater on each forest type. We also found significant differences among the forest types in terms of individual basal area and height, as well as density. Diversity increased along the environmental gradient, from flooded to well-drained forest. We conclude that variations in structure and diversity among the four forest types were correlated with the flooding regime, as well as with chemical and physical characteristics of the soil.