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Mountain glaciers are crucial sources of fresh water, contributing directly and indirectly to water, energy and food supplies for hundreds of millions of people. Assessing the impact of diminishing glacial meltwater contributions to the security of this resource is critical as we seek to manage and adapt to changing freshwater dynamics in a warming world. Both water quantity and quality influence water (in)security, so understanding the fluxes of water, sediment and contaminants through glacial and proglacial systems is required for holistic assessment of meltwater contribution to downstream resource security. In this paper we consider the socio-environmental role of and pressures on glacier-fed waters, discuss key research priorities for the assessment of both the quantity and quality of meltwater and reflect on the importance of situating our understanding within a transdisciplinary and inclusive research landscape. [ABSTRACT FROM AUTHOR]

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. 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. [ABSTRACT FROM AUTHOR]

Although Extreme El Niño Events (EENE) have always impacted hydrology in South America, their intensification by global warming and their association with changes in human activities and land cover may lead to the acceleration of sediment transfers in river systems and dam reservoirs. This situation may threaten soil and water resources in a region highly dependent on freshwater 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 on 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) for estimating the evolution of sedimentation rates and changes in sediment sources during the last five decades. Sediment tracing results indicated the occurrence of changes in sediment sources associated with positive and negative phases of the Central and East Pacific Index (C and E index), with a greater contribution of the lowland dry forest biome in comparison to that of the Andean source to sediment during the warm periods (El Niño events, ENE), (mean contribution of 76 %, up to 90 % during the Coastal El Niño Events (CENE) of 2016–2017). Overall, the development of agriculture within the fluvial plains of the dry forest biome upstream of the Poechos dam induced an acceleration of sedimentation rates by 140 % after 1997, with an accumulation of coarser sediment in the reservoir during ENE and EENE. This study suggests that the expansion of agriculture (e.g. agriculture in floodplains, deforestation) associated with a higher frequency of extreme rainfall events amplified the consequences of ENE, EENE and CENE on the quantity and quality of sediment transported by this river system, which will significantly decrease the lifespan of the dam reservoir essential to meet freshwater demands of the farmers and the populations living in this region. [ABSTRACT FROM AUTHOR]

Mountain glaciers are crucial sources of fresh water, contributing directly and indirectly to water, energy and food supplies for hundreds of millions of people. Assessing the impact of diminishing glacial meltwater contributions to the security of this resource is critical as we seek to manage and adapt to changing freshwater dynamics in a warming world. Both water quantity and quality influence water (in)security, so understanding the fluxes of water, sediment and contaminants through glacial and proglacial systems is required for holistic assessment of meltwater contribution to downstream resource security. In this paper we consider the socio-environmental role of and pressures on glacier-fed waters, discuss key research priorities for the assessment of both the quantity and quality of meltwater and reflect on the importance of situating our understanding within a transdisciplinary and inclusive research landscape. [ABSTRACT FROM AUTHOR]