El Niño–Southern Oscillation (ENSO)-driven hypersedimentation in the Poechos Reservoir, northern Peru
<p>Although extreme El Niño events (EENEs) have always impacted hydrological anomalies and sediment transport in South America, their intensification by global warming and their association with changes in human activities and land cover after humid periods may lead to the acceleration of sedi...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-09-01
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| Series: | Hydrology and Earth System Sciences |
| Online Access: | https://hess.copernicus.org/articles/27/3191/2023/hess-27-3191-2023.pdf |
| Summary: | <p>Although extreme El Niño events (EENEs) have always impacted
hydrological anomalies and sediment transport in South America, their
intensification by global warming and their association with changes in
human activities and land cover after humid periods may lead to the
acceleration of sediment transfers in river systems and dam reservoirs. This
situation may threaten soil and water resources in arid and semiarid regions
highly dependent on water originating from large dams. In this study, we
investigated the sediment sequence accumulated in the Poechos Reservoir
(northern Peru) and provided a retrospective reconstruction of the
interactions of El Niño–Southern Oscillation (ENSO), agricultural
practices and vegetation cover changes with sediment dynamics (1978–2019). To
this end, a sediment core was dated and characterized by physical and
chemical analyses (e.g., scanner tomography, X-ray fluorescence, particle
size analysis) to estimate the evolution of sedimentation rates and
changes in sediment sources during the last 5 decades.</p>
<p>Sediment tracing results indicated the occurrence of changes in sediment
sources associated with positive and negative phases of the Eastern Pacific
index with a greater contribution of the lowland dry-forest area in
comparison to that of the Andean area to sediment during the El Niño
events (mean contribution of 76 %; up to 90 % during the coastal El
Niño events (CENEs) of 2016–2017). This source contribution was mostly
controlled by the stationary rainfall occurring during the EENEs in the lowland dry-forest area characterized by a low vegetation cover. Overall, after an extreme phase of ENSO, like after the
EENE 1982–1983, the normal discharges and persistent sediment supplies from
the middle- and upper-catchment parts led to river aggradation and the
storage of substantial amounts of sediment in alluvial plains. In the
absence of a significant EENE between 1983 and 1997, the large volume of
sediment stored in the alluvial plains was exported by the EENE 1997–1998
resulting in an increase in sedimentation rate of 140 % after 1997 with
a significant aggradation of the deltaic zone of the reservoir. In addition
to the impact of extreme climate events on sediment dynamics, the
development of agriculture along the riverine system after an extreme phase
of ENSO increased the availability of sediments in the main channel of the
rivers, easily transported by the next EENE. This study suggests that
intensification of human activities associated with a higher frequency of
extreme rainfall events amplified the quantity of sediment transported by
the river system, which will significantly decrease the lifespan of the
reservoir, which is essential to meeting the freshwater demands of the farmers and the
populations living in this arid and semiarid region.</p> |
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| ISSN: | 1027-5606 1607-7938 |