Abstract ID: 241

A comparison between the components of hydrological cycle on micro-basins of primary forest and fragmented forest in the Central Amazon

One of the largest uncertainty factors of future scenarios of global climate is related to the feedback mechanisms among the land cover and hydrological components in the Amazon. It is still necessary to improve the knowledge of how the rainfall patterns are affected or redistributed by deforestation and/or regrowth of the vegetation. Studies regarding the impacts of vegetation change on climate and water balance are currently developed indicating that vegetation might have a significant influence on the streamflow hydrograph and water cycle. The shape of hydrographs depends on factors as topography, shape of the basin, soil, land cover and distribution, duration and intensity of precipitation. The objective of this work is to improve the understanding of the hydrological processes on micro-catchments that suffered deforestation and re-growth compared to undisturbed micro-catchment. The water balance components and hydrographs analysis of an undisturbed (6.46 km2) and a disturbed (~ 6 km2) basin are compared in order to evaluate the role of vegetation on them. Both catchments are located in the Central Amazon, near Manaus-AM. Average discharge was 4.0 mm.day-1 in the primary forest against 2.4 mm.day-1 (39% less) in the area covered by pasture and secondary forest. The rainfall measurements did not present such difference between undisturbed and disturbed areas, averaging 8.0 mm.day-1 and 7.4 mm.day-1, respectively. Applying a simplified water balance it was obtained an evapotranspiration of 3.4 mm.day-1 for the primary forest and 5.0 mm.day-1 for the fragmented area, inducing to believe in a higher evapotranspiration of regrowth vegetation. Unit hydrographs will be selected for distinct events on each site to a better knowledge of the water production, but preliminary analysis have shown that the base flow is responsible for around 68 % of the runoff in the undisturbed site and 85% in the disturbed area, what can point to a higher contribution of the direct flow on runoff in the primary forest than in secondary forest.

Session:  Feedbacks to Climate - Land cover, surface hydrology, and atmospheric feedbacks. (B)

Presentation Type:  Oral