Abstract
ABSTRACT The Atrato river basin is located in the Pacific fringe of Colombia, region with one of the highest precipitation rates in the world. The main purpose of this study is to determine the dominant processes in the hydrological responses along 17 sub-basins within the basin using principal component analysis. Watersheds located at the headwater presented a fast or medium response to the precipitation events, while higher flow homogeneity was observed in watersheds located at the lower portions of the basin. Three principal components were responsible for explaining 85.18% of the total variance. The component PC1 revealed the largest contributions for low flow behavior, being associated to precipitation, characteristic discharge values, compactness index, soil coverage and soil coarse textures. The component PC2 was assigned to the geological variables, fine and average texture soil and the average basin slope. Finally, the component PC3 has shown to be related to high flow patterns (maximum characteristic discharge values Q5 and Q1), igneous rocks and length of the basin. Highest specific discharge was associated to alluvial deposits and forest cover, whereas the slope was considered determinant for the run-off generation.
Highlights
In tropical and equatorial regions, the atmospheric convergence processes and moisture transport from the oceans are responsible for high rainfall events, which generate fast responses in water discharge in river channels (Strauch, 2013; Strauch et al, 2015)
In order to understand the hydrological controls of the Atrato river flow a key scientific question has been proposed: What are the most influential parameters that control the hydrological response of the sub-basins of the Atrato river and how to determine them? Having this question as a guideline, the objective of the present study is to identify and to characterize the physiographic and morphological variables that control the hydrological responses of the Atrato river sub-basins, based on data from a long term monitoring program (1984-2017)
The statistical analysis indicated the existence of two trends in the average precipitation magnitudes: (i) An increasing trend comprised of three stations; (ii) A decrease trend in the other two stations showing different significance levels
Summary
In tropical and equatorial regions, the atmospheric convergence processes and moisture transport from the oceans are responsible for high rainfall events, which generate fast responses in water discharge in river channels (Strauch, 2013; Strauch et al, 2015). Climate change prediction models (Gleeson et al, 2020) run for equatorial and tropical regions revealed a decrease in rainfall rates. Catchments located in these regions are, highly susceptible. Changes in their hydrological regime may impact the provision of regulatory ecosystem services. The Colombian territory is affected by three major sources of humidity: the Caribbean Sea, the Pacific Ocean and the Amazon rainforest. It presents a complex climate configuration, with remarkable spatiotemporal variations of precipitation associated to a large physiographic variability. Recent simulations revealed water scarcity risk scenarios for the Andean region and flooding in the coastal regions associated with sea level rise (Intergovernmental Panel on Climate Change, 2014a, 2014b; Hurtado & Mesa, 2015; Pardo & Alfonso, 2018)
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