Heterogeneity in Spatiotemporal Variability of High Mountain Asia's Runoff and Its Underlying Mechanisms

Abstract

High Mountain Asia (HMA) is the headwater area for major Asian rivers, providing a vast amount of freshwater to billions of people in Asia. These rivers also make their surrounding areas highly vulnerable to destructive water‐related disasters. However, the complex spatiotemporal variability of runoff over HMA and its underlying mechanisms are poorly understood. This study investigates into the spatial heterogeneity of HMA's runoff variability at three timescales (interannual, interdecadal, and multidecadal) and the roles played by climate conditions and catchment properties. We find significant interannual and multidecadal variability of runoff in west and central HMA, and significant interdecadal variability in central and east HMA. At interannual and multidecadal timescales, the runoff variability tends to be more significant in dryer basins. The variability of runoff at the three timescales is largely controlled by climate variations, especially precipitation. The catchment properties, including groundwater storage and glacier‐snow meltwater, also play important roles in regulating the effect of precipitation. In particular, the high contributions of glacier‐snow meltwater in east HMA can weaken the response of runoff variability to precipitation at interannual and multidecadal timescales. The space‐time patterns of runoff variability over HMA are driven by atmospheric drivers including El Niño‐Southern Oscillation, Interdecadal Pacific Oscillation, and Atlantic Multidecadal Oscillation across timescales. The results of this study provide a better understanding of HMA's runoff variability and its physical mechanisms, which have critical implications for sustainable freshwater management and effective risk mitigation in this densely populated and ecologically vulnerable region.

Enhancing Watershed Management through Adaptive Source Apportionment under Changing Environment

“…When the periodic trend of annual precipitation exhibits a change of 1mm, nitrogen and phosphorus emissions increase by 2354t and 287.14t, respectively (Supplementary Table 4). Temporal variations of nitrogen concentrations in surface water are predominantly dictated by seasonal climate changes, particularly during nutrient application periods [38][39][40] . Moreover, excessive manure application to meet crop demands may adversely affect soil phosphorus conditions.…”

Evolutionary Characteristics of Daytime and Nocturnal Precipitation Heterogeneity in Gansu Province, Northwest China

“…Why do these high-altitude zones generally have a more prominent performance? This must be the result of the interaction of faster warming rates, larger daily temperature ranges, more abundant water vapor sources, and other factors [12,18,22]. For example, the special topography is conducive to blocking the increasing abundance of external water vapor in the atmospheric circulation, and favorable hydrological conditions can make full use of the local internal circulation of water vapor.…”

“…As a sensitive area and a significant area of impact of global climate change, the level of warming in China was higher than the global average for the same period, reaching 0.16 • C/10 a (per decade) between 1901 and 2022 [2]. With global warming, not only is the water cycle undergoing many changes [3][4][5][6], but also droughts, hot extremes [7][8][9], heavy precipitation, floods [10][11][12], and various secondary disaster events [13][14][15] are occurring frequently around the world. For example, from the night of 29 July to the early morning of 2 August 2023, Beijing suffered its worst rainstorm in nearly 140 years (Beijing Meteorological Bureau); in July 2018, heavy rainstorms in western Japan killed more than 220 people, and so on.…”