Streamflow Elasticity to Precipitation Distribution and Potential Evapotranspiration Across South America

ABSTRACT This study examines the sensitivity of mean, high and low streamflows (i.e., Q elasticity) to changes in precipitation (P) and potential evapotranspiration (PET) across South America. The response to P was further assessed by intensifying its seasonal and daily distribution, specifically by increasing (decreasing) P during wet (dry) periods and high (low) events, while maintaining the annual P volume unchanged. Simulations from a continental‐scale hydrological model indicate that Q exhibits a stronger response to increases in P than to decreases. Arid and semi‐arid regions exhibited the highest Q elasticities and amplification of changes in P and PET, whereas in humid regions these effects were lower in magnitude. PET impacts were strongest on low flows ( Q low ) in the Caatinga and on mean/high flows ( Q mean / Q high ) in Pantanal and Pampa biomes. The Q response to P depends not only on the amount of rainfall but also on how and when it occurs. Seasonal intensification reduced Q low (median −6%) and increased Q mean (+4%) and Q high (+12%), whereas daily intensification yielded −6%, +3% and +6% for Q low , Q mean and Q high , respectively, in response to a 20% alteration in P distribution. Sensitivity to seasonal P distribution scaled with baseline seasonality, and unimodal regimes exhibited larger seasonal elasticities than bimodal regimes. Overall, in seasonal regions, the seasonal redistribution of P has stronger effects on extreme flows. Accordingly, streamflow elasticity provides a quantitative framework to assess regional and biome‐specific responses to climate variability and to inform projections of hydrological change across watersheds.