Hydrological effects of climate variability and vegetation dynamics on annual fluvial water balance in global large river basins

Liu, Jianyu; Zhang, Qiang; Singh, Vijay P.; Song, Changqing; Zhang, Yongqiang; Sun, Peng; Gu, Xihui

The partitioning of precipitation into runoff (inline-formulaR) and evapotranspiration (inline-formulaE), governed by the controlling parameter in the Budyko framework (i.e., inline-formulan parameter in the Choudhury and Yang equation), is critical to assessing the water balance at global scale. It is widely acknowledged that the spatial variation in this controlling parameter is affected by landscape characteristics, but characterizing its temporal variation remains yet to be done. Considering effective precipitation (inline-formulaPe), the Budyko framework was extended to the annual water balance analysis. To reflect the mismatch between water supply (precipitation, inline-formulaP) and energy (potential evapotranspiration, inline-formulaE0), we proposed a climate seasonality and asynchrony index (SAI) in terms of both phase and amplitude mismatch between inline-formulaP and inline-formulaE0. Considering streamflow changes in 26 large river basins as a case study, SAI was found to the key factor explaining 51 % of the annual variance of parameter inline-formulan. Furthermore, the vegetation dynamics (inline-formulaM) remarkably impacted the temporal variation in inline-formulan, explaining 67 % of the variance. With SAI and inline-formulaM, a semi-empirical formula for parameter inline-formulan was developed at the annual scale to describe annual runoff (inline-formulaR) and evapotranspiration (inline-formulaE). The impacts of climate variability (inline-formulaPe, inline-formulaE0 and SAI) and inline-formulaM on inline-formulaR and inline-formulaE changes were then quantified. Results showed that inline-formulaR and inline-formulaE changes were controlled mainly by the inline-formulaPe variations in most river basins over the globe, while SAI acted as the controlling factor modifying inline-formulaR and inline-formulaE changes in the East Asian subtropical monsoon zone. SAI, inline-formulaM and inline-formulaE0 have larger impacts on inline-formulaE than on inline-formulaR, whereas inline-formulaPe has larger impacts on inline-formulaR.

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Liu, Jianyu / Zhang, Qiang / Singh, Vijay P. / et al: Hydrological effects of climate variability and vegetation dynamics on annual fluvial water balance in global large river basins. 2018. Copernicus Publications.

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