Hydrologic Sensitivities and ENSO Variability Across Hydrological Regimes in Central Chile (28 degrees-41 degrees S)

There is strong evidence of El Nino-Southern Oscillation (ENSO) teleconnections in the South Pacific and related impacts on the precipitation regime in Chile; nonetheless, many aspects of the hydrological propagation and temperature responses to ENSO remain unclear in this region. We examine fluctuations across 59 near-natural catchments in central Chile (28 degrees-41 degrees S) under contrasting ENSO phases during the period 1981-2019. Our results show statistically significant ENSO-related hydroclimatic anomalies in almost all watersheds analyzed, which confirms the major influence of ENSO within this domain. By comparing El Nino phases against La Nina, we observe generally wetter conditions, warmer winters, cooler late springs, lower (higher) runoff ratios in snowmelt-driven (rainfall-driven) basins, and longer storm durations while storm frequencies (i.e., number of events of consecutive days with precipitation) are preserved. Additionally, low (high) elevation catchments are related to positive (negative) streamflow sensitivities to winter temperature, which increase in magnitude with the evaporative index; besides, catchments with sharp warm-and-dry conditions yield largely negative sensitivities to late spring temperature. Further, positive streamflow anomalies in rainfall-driven catchments are explained by temperature and precipitation ENSO-related amplitudes (El Nino minus La Nina) that separately favor streamflow; however, in mixed regimes and snowmelt-driven basins these results are spatially scattered. Hence, this study supports that meteorological, hydrological, and physiographic attributes modulate the translation of climate variability into river hydrology. The results presented here unravel the joint effects of precipitation and seasonal temperature fluctuations through different hydrological regimes, across a region that encloses populated cities and water-intensive activities.