Distribution and erosive potential of rainfall in the state of Tocantins, Brazil

Abstract

The objective of this work was to determine rainfall erosivity values and to generate its spatial‑temporal distribution maps in the state of Tocantins, Brazil. Pluviometric historical series from 97 rain gauges were analyzed, covering the period from 1985 to 2009. Erosivity was estimated by equations in which the independent variable was the average monthly rainfall or the Fournier rainfall index (Rc). Geostatistics was applied for mapping erosivity both monthly and annually. Annual erosivity values varied between 6,599 and 14,000 MJ mm ha^-1 h^-1, with peak in December when it reached values up to 2,800 MJ mm ha^-1 h^-1 per month. From May to September, erosivity values had lower than the critical one, considered 500 MJ mm ha^-1 h^-1 per month. Three priority regions were identified for soil and water conservation planning activities: mid‑west region of the state, in the neighborhood of Cantão State Park, with greatest erosivity; northern region of the state, especially during the first quarter of the year; and southern region of the state, in the fourth quarter.