From drought to flooding: understanding the abrupt 2010–11 hydrological annual cycle in the Amazonas River and tributaries

Abstract

In this work we document and analyze the hydrological annual cycles characterized by a rapid transition between low and high flows in the Amazonas River (Peruvian Amazon) and we show how these events, which may impact vulnerable riverside residents, are related to regional climate variability. Our analysis is based on comprehensive discharge, rainfall and average suspended sediment data sets. Particular attention is paid to the 2010-11 hydrological year, when an unprecedented abrupt transition from the extreme September 2010 drought (8300 m 3 s −1 ) to one of the four highest discharges in April 2011 (49 500 m 3 s −1 ) was recorded at Tamshiyacu (Amazonas River). This unusual transition is also observed in average suspended sediments. Years with a rapid increase in discharge are characterized by negative sea surface temperature anomalies in the central equatorial Pacific during austral summer, corresponding to a La Niña-like mode. It originates a geopotential height wave train over the subtropical South Pacific and southeastern South America, with a negative anomaly along the southern Amazon and the southeastern South Atlantic convergence zone region. As a consequence, the monsoon flux is retained over the Amazon and a strong convergence of humidity occurs in the Peruvian Amazon basin, favoring high rainfall and discharge. These features are also reported during the 2010-11 austral summer, when an intense La Niña event characterized the equatorial Pacific.

<strong>Drought and </strong><strong>wet episodes in Amazonia: the role of atmospheric moisture transport</strong>

“…Consequently, the ARB is the home of a high biodiversity and an important source of natural resources for human economic development, playing an important role in the regional and global hydrological cycle. Recent studies have investigated the hydrological cycle at the ARB, confirming the occurrence of several extreme hydrological events like droughts, floods, and a marked terrestrial water storage variability during the last years [1][2][3][4][5]. Future scenarios of a complete deforestation in the region point to a restrained water cycle [6,7].…”

Monitoring Rainfall Patterns in the Southern Amazon with PERSIANN-CDR Data: Long-Term Characteristics and Trends

“…For example, farmers interviewed in the state of Mato Grosso are worried about the intensification of extremely dry (veranico) or extreme rainfall events during the rainy season that may affect crops or jeopardize the harvest. It is not unusual to have dry periods during the rainy season corresponding to the "break phase" of the SAMS [31,74], and even droughts and floods are part of the natural variability of the system [75,76] and often occur in response to sea-surface temperature (SST) anomalies. However there has been indication of an increasing tendency to extreme seasonal drought or flood occurrences in the Amazon basin [19,39,77,78], including in the southern Bolivian Amazon [40].…”

Vulnerability and adaptive capacity of community food systems in the Peruvian Amazon: a case study from Panaillo

“…Prior to the 2010-2011 rainy season, the Peruvian Amazon was characterized by a severe drought, which unprecedentedly transitioned into one of the highest river discharges recorded in the area in April 2011 (Espinoza et al, 2012; See Figure 9). In the month of February 2011, 473 mm of rain fell in Ucayali, exceeding the February average of 279 mm (Vásquez et al, 2012).…”