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
Abstract
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.