ARTÍCULO
Tracking spatial variation in river load from Andean highlands to inter-Andean valleys
Fecha
2018Registro en:
0169555X
10.1016/j.geomorph.2018.02.009
Autor
Tenorio , Gustavo E.
Vanacker, Veerle
Campforts, Benjamin
Alvarez, Lenin
Zhiminaicela Saquinaula, Cesar Santiago
Vercruysse, Kim
Molina Verdugo, Armando
Govers, Gerard
Institución
Resumen
Mountains play an important role in the denudation of continents and transfer erosion and weathering products
to lowlands and oceans. The rates at which erosion and weathering processes take place in mountain regions
have a substantial impact on the morphology and biogeochemistry of downstream reaches and lowlands. The
controlling factors of physical erosion and chemical weathering and the coupling between the two processes
are not yet fully understood. In this study, we report physical erosion and chemical weathering rates for five
Andean catchments located in the southern Ecuadorian Andes and investigate their mutual interaction. During
a 4-year monitoring period, we sampled river water at biweekly intervals, and we analyzed water samples for
major ions and suspended solids. We derived the total annual dissolved, suspended sediment, and ionic loads
from the flow frequency curves and adjusted rating curves and used the dissolved and suspended sediment
yields as proxies for chemical weathering and erosion rates.
In the 4-year period of monitoring, chemical weathering exceeds physical erosion in the high Andean
catchments. Whereas physical erosion rates do not exceed 30 t km−2 y−1 in the relict glaciated morphology,
chemical weathering rates range between 22 and 59 t km−2 y−1
. The variation in chemical weathering is
primarily controlled by intrinsic differences in bedrock lithology. Land use has no discernible impact on the
weathering rate but leads to a small increase in base cation concentrations because of fertilizer leaching in surface
water. When extending our analysis with published data on dissolved and suspended sediment yields from the
northern and central Andes, we observe that the river load composition strongly changes in the downstream
direction, indicating large heterogeneity of weathering processes and rates within large Andean basins.