Abstract
Abstract. Hydro-sedimentology development is a great challenge in Peru due to limited data as well as sparse and confidential information. This study aimed to quantify and to understand the suspended sediment yield from the west-central Andes Mountains and to identify the main erosion-control factors and their relevance. The Tablachaca River (3132 km2) and the Santa River (6815 km2), located in two adjacent Andes catchments, showed similar statistical daily rainfall and discharge variability but large differences in specific suspended-sediment yield (SSY). In order to investigate the main erosion factors, daily water discharge and suspended sediment concentration (SSC) datasets of the Santa and Tablachaca rivers were analysed. Mining activity in specific lithologies was identified as the major factor that controls the high SSY of the Tablachaca (2204 t km2 yr−1), which is four times greater than the Santa's SSY. These results show that the analysis of control factors of regional SSY at the Andes scale should be done carefully. Indeed, spatial data at kilometric scale and also daily water discharge and SSC time series are needed to define the main erosion factors along the entire Andean range.
Highlights
Understanding erosion-control factors is a great challenge that would improve the modelling of climate-change impacts on mountain range dynamics or human impacts on the environment
This study showed that suspended-sediment yield (SSY) had a linear relation with slope and runoff above and below threshold values related to vegetation cover, respectively
This study focuses on two stations of the Santa River that are geographically close to each other (Fig. 1): the Santa station (507 m a.s.l.), covering the middle and upper Santa catchment (6815 km2), and the Tablachaca station (524 m a.s.l.), which monitors the whole Tablachaca sub-catchment (3132 km2)
Summary
Understanding erosion-control factors is a great challenge that would improve the modelling of climate-change impacts on mountain range dynamics or human impacts on the environment. There is intense human activity such as small- and large-scale mining of coal, metal and aggregates distributed from the coast to the highlands (Morera, 2010) In analysing this exceptional SSC dataset, we identify two adjacent catchments that have significant differences in their SSY despite having similar climatic and hydrologic contexts. This is a good example for improving understanding about which factors control the magnitude and frequency of SSY from the west-central Andes to the Pacific coast, with a special focus on (i) spatial differences in sediment production at the basin scale (few thousand km2), (ii) non-climatic erosion factors such as mine activity in specific lithology, and (iii) the relevant resolution of maps necessary to define erosion factors in the central Andes. Natural setting of the Tablachaca sub-watershed with strong altitudinal gradient creates highly vulnerable watersheds with deeper and smaller rivers than the Santa sub-watershed
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