Abstract
Abstract. Since 2010 an uninterrupted sequence of dry years, with annual rainfall deficits ranging from 25 to 45 %, has prevailed in central Chile (western South America, 30–38° S). Although intense 1- or 2-year droughts are recurrent in this Mediterranean-like region, the ongoing event stands out because of its longevity and large extent. The extraordinary character of the so-called central Chile megadrought (MD) was established against century long historical records and a millennial tree-ring reconstruction of regional precipitation. The largest MD-averaged rainfall relative anomalies occurred in the northern, semi-arid sector of central Chile, but the event was unprecedented to the south of 35° S. ENSO-neutral conditions have prevailed since 2011 (except for the strong El Niño in 2015), contrasting with La Niña conditions that often accompanied past droughts. The precipitation deficit diminished the Andean snowpack and resulted in amplified declines (up to 90 %) of river flow, reservoir volumes and groundwater levels along central Chile and westernmost Argentina. In some semi-arid basins we found a decrease in the runoff-to-rainfall coefficient. A substantial decrease in vegetation productivity occurred in the shrubland-dominated, northern sector, but a mix of greening and browning patches occurred farther south, where irrigated croplands and exotic forest plantations dominate. The ongoing warming in central Chile, making the MD one of the warmest 6-year periods on record, may have also contributed to such complex vegetation changes by increasing potential evapotranspiration. We also report some of the measures taken by the central government to relieve the MD effects and the public perception of this event. The understanding of the nature and biophysical impacts of the MD helps as a foundation for preparedness efforts to confront a dry, warm future regional climate scenario.
Highlights
Droughts have been recognized as a major climate hazard in many regions worldwide (e.g., Mishra and Singh, 2010; Seneviratne et al, 2012)
A preliminary survey conducted by our group found significant impacts of this protracted drought on surface hydrology, groundwater, sediment exportation into the ocean, vegetation and fire activity along central Chile (CR2, 2015), and we show later that such a multi-year drought is already unprecedented in the historical record and quite unusual in the last millennium
While intense but short-lived (1–2-year long) droughts are a recurrent feature in the Mediterranean-like climate of this region, the recent event has several distinct features supporting its denomination as the central Chile megadrought (MD)
Summary
Droughts have been recognized as a major climate hazard in many regions worldwide (e.g., Mishra and Singh, 2010; Seneviratne et al, 2012). Depending on its duration and intensity, a lower-than-average precipitation condition (i.e., a meteorological drought) can lead to a substantial decrease in surface water resources, soil moisture and groundwater, causing a multiplicity of adverse ecological, social and economic impacts (see a review in Wilhite, 2000). Semi-arid, Mediterranean-like regions are prone to droughts given that most of the annual rainfall accumulation is accounted for in a few events, so that individual missed storms. Garreaud et al.: The 2010–2015 megadrought in central Chile can have a significant impact (e.g., Ragab and Prudhomme, 2002; Rockström et al, 2010)
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