Browsing by Author "Gutierrez Cori, Omar"

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    Decline of fine suspended sediments in the Madeira River Basin (2003–2017)
    (MDPI, 2019-03-12) Ayes Rivera, Irma; Armijos Cardenas, Elisa Natalia; Espinoza Villar, Raúl Arnaldo; Espinoza, Jhan Carlo; Molina-Carpio, Jorge; Max Ayala, José; Gutierrez Cori, Omar; Martinez, Jean-Michel; Filizola, Naziano
    The Madeira River is the second largest Amazon tributary, contributing up to 50% of the Amazon River’s sediment load. The Madeira has significant hydropower potential, which has started to be used by the Madeira Hydroelectric Complex (MHC), with two large dams along the middle stretch of the river. In this study, fine suspended sediment concentration (FSC) data were assessed downstream of the MHC at the Porto Velho gauging station and at the outlet of each tributary (Beni and Mamoré Rivers, upstream from the MHC), from 2003 to 2017. When comparing the pre-MHC (2003–2008) and post-MHC (2015–2017) periods, a 36% decrease in FSC was observed in the Beni River during the peak months of sediment load (December–March). At Porto Velho, a reduction of 30% was found, which responds to the Upper Madeira Basin and hydroelectric regulation. Concerning water discharge, no significant change occurred, indicating that a lower peak FSC cannot be explained by changes in the peak discharge months. However, lower FSCs are associated with a downward break in the overall time series registered at the outlet of the major sediment supplier—the Beni River—during 2010.
    Palabras clave:Madeira RiverFine suspended sediment concentrationsWater discharge
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    Evolution of wet‐day and dry‐day frequency in the western Amazon basin: relationship with atmospheric circulation and impacts on vegetation
    (American Geophysical Union (AGU), 2016-11) Espinoza, Jhan Carlo; Segura Cajachagua, Hans Mikhail; Ronchail, Josyane; Drapeau, Guillaume; Gutierrez Cori, Omar
    This paper documents the spatiotemporal evolution of wet‐day and dry‐day frequency (WDF and DDF) in the western Amazon, its relationships with oceanic and atmospheric variability and possible impact on vegetation. WDF and DDF changed significantly during the 1980–2009 period (p < 0.05). An increase in WDF is observed after 1995 over the northern part of the western Amazon (Marañón basin). The average annual value of WDF changed from 22 days/yr before 1995 to 34 days after that date (+55% after 1995). In contrast, DDF increased significantly over the central and southern part of this region (Ucayali basin) after 1986. Average annual DDF was 16.2 days before 1986 and 23.8 days afterward (+47% after 1986). Interannual variability in WDF appears to be modulated by changes in Pacific SST and the Walker cell during the November–March season. This mechanism enhances convective activity over the northern part of the western Amazon. The increase in DDF is related to warming of the North Tropical Atlantic SST, which produces changes in the Hadley cell and subsidence over the central and the southern western Amazon. More intense seasonal hydrological extremes in the western Amazon therefore appear to be related to changes in WDF and DDF that occurred in 1995 and 1986, respectively. During the 2001–2009 period, an index of vegetation condition (NDVI) appears negatively correlated with DDF (r = −0.95; p < 0.0001). This suggests that vegetation in the western Amazon is mainly water limited, rather than light limited and indicates that the vegetation is highly sensitive to concentration of rainfall.
    Palabras clave:RainfallAmazon‐AndesPeru