Coherent streamflow variability in Monsoon Asia over the past eight centuries---links to oceanic drivers

Abstract

Climate-informed dynamic streamflow reconstruction is skillful over most of Monsoon Asia • Spatial coherence of streamflow suggests water management be coordinated among basins • Mekong and Chao Phraya are most sensitive among rivers to anomalies in sea surface temperature AbstractThe Monsoon Asia region is home to ten of the world's biggest rivers, supporting the lives of 1.7 billion people who rely on streamflow for water, energy, and food. Yet, a synoptic understanding of multi-centennial streamflow variability for this region is lacking. Here we produce the first large scale streamflow reconstruction over Monsoon Asia (63 stations in 16 countries), using a novel climate-informed dynamic algorithm that is skillful over 92% of the gauging stations. We show that streamflow in Monsoon Asia is spatially coherent, owing to common drivers from the Pacific, Indian, and Atlantic Oceans that exert their greatest influence over the Mekong and Chao Phraya basins. This work increases our understanding of streamflow variability over Monsoon Asia. We suggest that future water management in the region should be coordinated between basins, taking into account the states of the oceans. * This manuscript is undergoing revision; it may be updated in a near future.

The Greater Mekong's Climate‐Water‐Energy Nexus: How ENSO‐Triggered Regional Droughts Affect Power Supply and CO2 Emissions

“…Yet, conclusions drawn on the grid's exposure and response to hydroclimatic variability should be taken with caution, owing to the nonstationarity in the ENSO‐monsoon teleconnection. Analyses conducted over the past centuries—combining observed and paleo‐reconstructed data—revealed that the strength of the teleconnection varied over space and time, alternating decades of weaker and stronger effects (Nguyen et al., 2020; Räsänen et al., 2016). An explanation for this behavior may be sought in the amplitude, temporal evolution, and spatial patterns of ENSO events.…”

“…Warm conditions in the tropical Pacific (El Niño) delay the monsoon onset and shorten the overall rain season, while cold conditions (La Niña) are associated to wetter conditions in mainland Southeast Asia (Cook & Buckley, 2009; Singhrattna et al., 2005). Third, streamflow in the Mekong and Chao Phraya river basins is spatially coherent, owing to common meteorological and climatological drivers (Nguyen et al., 2020). We thus expect water availability and dispatchable hydropower to show seasonal and interannual modes of variability in both basins.…”

Flood mortality in SE Asia: Can palaeo‐historical information help save lives?

“…The results of these reconstructions portend a potential increase in flood events in the future, depending on how these large-scale climate phenomena are affected by climate change (Cai, Sullivan, & Cowan, 2009;Perry, Mcgregor, Gupta, & England, 2017;Zhang & Delworth, 2016). Further, the streamflow reconstructions provide an extended flow dataset ranging from 247 to 800 years in length to test and improve FFA methods (D'Arrigo et al, 2011;Nguyen et al, 2020;Nguyen & Galelli, 2018).…”

“…The phases of ENSO, the Indian Ocean Dipole (IOD), and the Pacific Decadal Oscillation (PDO) all influence the strength and occurrence of the monsoons and tropical storms in SE Asia. In a recent analysis, the reconstruction of 800 years of streamflow in several rivers by Nguyen, Turner, Buckley, and Galelli (2020) was useful in showing that streamflow in Monsoon Asia is spatially coherent, with concurrent high/low flow episodes in adjacent basins because ENSO, IOD, PDO, and tropical Atlantic sea‐surface temperatures are common drivers. Collectively, the effect of these phenomena, often in tandem, vary in location, magnitude and timing, such that extremes are not likely captured in short flow records.…”

“…The results of these reconstructions portend a potential increase in flood events in the future, depending on how these large‐scale climate phenomena are affected by climate change (Cai, Sullivan, & Cowan, 2009; Perry, Mcgregor, Gupta, & England, 2017; Zhang & Delworth, 2016). Further, the streamflow reconstructions provide an extended flow dataset ranging from 247 to 800 years in length to test and improve FFA methods (D'Arrigo et al, 2011; Nguyen et al, 2020; Nguyen & Galelli, 2018). Finally, New research on the Ping River in northern Thailand, however, has revealed that a flood in 1,831 CE enlarged the channel with a bankfull discharge (not including overflows) of 11,000 m 3 /s, a rate that is larger than the maximum flow ever gauged in Chiang Mai by more than an order of magnitude (Wasson, unpublished).…”