Hydroclimatic variability across Mongolia's breadbasket and implications for water resource management

Meteorological records from Mongolia suggest that precipitation is highly variable across the landscape and that recent hydroclimatic trends differ spatially. New developments in agriculture, mining, and other economic sectors demanding water resources in Mongolia will require a better understanding of how hydroclimate varies in time and space. Using a rotated principal components analysis (RPCA) with an annually-resolved network of tree-ring data, we have identified four distinct hydroclimatic regions from 1790-1994 across north-central Mongolia. Thus far, these regions have been represented in three streamflow reconstructions: the Kherlen, Selenge, and Yerru River reconstructions. The Selenge and Yeruu streamflow reconstructions encompass the "breadbasket" region of Mongolia, which has seen a recent influx of agricultural practices. The Yeruu River reconstruction is the most recently developed and consists of six drought-sensitive chronologies within the breadbasket region while accounting for 60.8% of the instrumental streamflow variability during the calibration period (1959-1987). The Selenge and Yeruu streamflow reconstructions, representing the western and eastern portions of the breadbasket respectively, are similar in that they share some historical drought and pluvial periods. Further, both reconstructions suggest that the 20th century is wetter than prior centuries. However, the Selenge and Yeruu are also markedly different in that Yeruu streamflow has a more stable distribution of hydroclimate over time, whereas Selenge streamflow has more prominent and extreme shifts in hydroclimatic regimes over the past several centuries. These findings have important implications for managing water resources in the future by suggesting that a) recent droughts in Mongolia, though severe, were not as severe as some droughts in the past, but might appear more extreme due to preceding wet conditions during the early-to-mid 20th century, and b) hydroclimatic stability can differ over space.