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A decrease in river discharge and rainfall amount, from a 100-year data set, in response to El Niño events on the interannual temporal scale for the Philippines
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  • Natasha Sekhon,
  • CP David,
  • Mart Cyrel M. Geronia,
  • Manuel Justin G. Custado,
  • Daniel Enrique Ibarra
Natasha Sekhon
Brown University

Corresponding Author:natasha_sekhon@brown.edu

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CP David
University of the Philippines Diliman
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Mart Cyrel M. Geronia
National Institute of Geological Sciences
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Manuel Justin G. Custado
National Institute of Geological Sciences, University of the Philippines, Diliman
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Daniel Enrique Ibarra
Brown University
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The El Niño Southern Oscillation (ENSO) modulates rainfall amount variability and, by extension, river discharge in the Philippines on seasonal to interannual temporal scales. The El Niño phase (ENP) of ENSO considerably decreases rainfall amounts on a seasonal scale in the western Pacific with varying degrees of heterogeneity expressed across the Philippines. Our understanding of the response in the hydroclimate to ENPs on interannual timescales is still relatively immature. As such, to investigate the hydroclimate response, a composite time series of 29 rainfall and 61 river discharge stations spanning 1901-2020 and 1908-2017 C.E., respectively, and covering the four major climate types in the Philippines were assessed. Our results suggest, regardless of climate type, that river discharge and rainfall data decrease following ENPs. The median response suggests that the decreasing trend can last up to seven years. Further, the hydroclimate response follows either a decreasing trend, if at conception of an ENP, or an increasing trend, if at the termination of an ENP. As water-scarcity becomes an area of immediate concern in an increasingly warming climate, our results have implications for interannual water resource management in this drought-prone tropical archipelago.