Multi-annual variability of streamflow in La Plata Basin. Part I: observations and links to global climate

Relationship between rainfall and streamflow in the La Plata Basin: annual cycles, interdecadal and multidecadal variability

“…interdecadal and multidecadal variability, respectively) in streamflow compared to precipitation. This method was previously applied in several studies to analyse air temperature and precipitation cycles and to capture streamflow low frequency variability modes and pseudo-periodic patterns (Leite and Peixoto, 1995;Maciel et al, 2013;Li et al, 2015). The main feature of MEM, compared to the other available methodologies, is to assume that the time series of interest follow an autoregressive process of order p (AR(p)) -whose coefficients are estimated from observations-and takes advantage of the exact mathematical relationship between these and the theoretical spectral density of the AR processes (Box and Jenkins, 1994;Ghil et al, 2002) for extracting a smooth spectrum.…”

“…Different aspects of the hydroclimatic variability and trends in the LPB have been addressed by several authors (Garcia and Vargas, 1996;Tucci and Clarke, 1998;Krepper et al, 2006;Doyle and Barros, 2011;Maciel et al, 2013;Antico et al, 2014;Boulanger et al, 2016;Lovino et al, 2018, Shi et al, 2019, Zanin and Satyamurty, 2020a2020b). In the last decades the discharge interannual variability of the main rivers of the LPB and its climate forcing have also been analyzed (Mechoso and Perez-Iribarren, 1992;Depetris et al, 1996;Garcia and Vargas, 1996;Genta et al, 1998;Robertson and Mechoso, 1998;, Bischoff et al, 2000Camilloni and Barros, 2000;Berri et al, 2002;Krepper et al, 2003, among others).…”

“…Results from both studies showed that lower Paraguay River basin presents a near decadal cycle while the Parana River in Posadas discharge gauging station is modulated by a cycle of around 9 years. Maciel et al (2013) studied the multi-annual variability of observed streamflows for Parana, Paraguay and Negro rivers during the 20 th century. Results from their analysis presented significant low frequency variability with increasing trends that showed a clear seasonality in the three rivers.…”

The Role of Land Cover in the Propagation of Rainfall Into Streamflow Trends

“…Recently, Bartiko et al (2017) also found clusters of increasing annual maximum daily flow in the Upper Uruguay basin. However, since large water flows in SB are linked to recurrent climatic features such as the ENSO phenomena (Krepper et al, 2003;Maciel et al, 2013;Pasquini & Depetris, 2007;Robertson & Mechoso, 1998;Silva et al, 2017), the nonstationarity in the flood time series might be related to oscillatory components rather than to a linear trend. Analyses in other regions of the world show that changes in floods follow highly oscillatory components and are concentrated in specific periods in time, with flood-rich and flood-poor periods (Blöschl et al, 2015;Hall et al, 2014).…”

“…In Southern Brazil (SB) there were increases in annual average, minimum, and maximum streamflow (Bartiko et al, 2017;Berbery & Barros, 2002;Detzel et al, 2016;Doyle & Barros, 2011;Hirata et al, 2010;Marques, 2012;Pasquini & Depetris, 2007), generally associated with rainfall variability (Doyle & Barros, 2011;Maciel et al, 2013;Saurral et al, 2008). The Uruguay and the Paraná rivers, which downstream become the La Plata River, have experienced in the last century one of the greatest annual streamflow increases in the world (Milliman et al, 2008;Piao et al, 2007).…”