Estimativa da erosividade de chuva na Bacia Hidrográfica do Rio Zambeze: caso de estudo da área da bacia que abrange Moçambique

Abstract

This study estimated rainfall erosivity in the Zambezi Basin to identify the areas most vulnerable to erosion. To this end, the erosivity index was determined based on spatial precipitation data from the CHIRPS platform, and the return period of an erosion event was also determined. The methodology is based on monthly precipitation averages. To calculate annual erosivity, the monthly precipitation averages for each year were considered, and map algebra was subsequently applied in ArcGIS 10.1. Conversely, for the rainy season, the monthly precipitation averages for each month were considered. The results reveal spatial fluctuations in the erosivity index, with greater emphasis on the upstream and downstream sides of the basin. For the annual erosivity index, the lowest value corresponds to 1,467.2 MJ.mm/(ha.year) and the highest, 4,473.85 MJ.mm/(ha.year), with a range of 3,000.65 MJ.mm/(ha.year). These values ​​classify this region as having low and medium erosivity. Furthermore, during the rainy season, November and April present lower values, while December, January, February, and March present higher values. It is important to emphasize that the dry season was distinguished based on the low rainfall observed at that time of year. Additionally, the return period and the probability of erosive events were calculated for the same study period. A higher index of 5,366.578 MJ.mm/(ha.year) is interpreted as medium erosivity. Finally, the study highlights areas of medium and low erosivity, and the characteristics of the relief and vegetation amplify this phenomenon.