Dynamics of deforestation in Amazonia and its impacts in hydrology: Machadinho River basin - Rondônia / Brazil

Abstract

The Machadinho river basin is an example of disorderly occupation present in the Amazon region, where large areas were deforested and consequently the forest was converted into pastures and urban centers. The present work has the objective of analyzing the impacts in hydrology (streamflows, precipitation and evapotranspiration) of the Machadinho river basin due to its dynamics of anthropic occupation. First, the land cover change was analyzed using Landsat 5-TM images for the years 1984, 1997 and 2011. The streamflow variable was evaluated for its sensitivity by using the SWAT model to determine net discharge by setting the weather patterns and by varying the historical land cover scenarios. The precipitation, obtained by data from the CHIRPS for the period from 1981 to 2017, and evapotranspiration, estimated by the SSEBop data between 2002 and 2017, were treated as distributed geospatial variables in the basin, with behavioral trends of their corresponding historical series measured by means of the Mann-Kendal test. The results showed that the occupation of the basin occurred in a disorderly way, where the pasture area increased from 2.6% in 1984 to 45.9% in 2011, with the highest conversion observed at the spring of the main water body, which accounted for a higher flow production by the SWAT model that adequately described the variable. In addition, trends of rainfall reduction were observed in wetter months, while trends of evapotranspiration elevation were detected in warmer months. Therefore, it is noteworthy to register that deforestation in the region tends to reduce water availability to the basin.

Keywords:
Anthropogenic impacts; Amazon region; Hydrology; Hydrological modeling.