Runoff Dynamics and Associated Multi-Scale Responses to Climate Changes in the Middle Reach of the Yarlung Zangbo River Basin, China

Abstract

Long-term hydro-climatic datasets and sophisticated change detection methods are essential for estimating hydro-climatic trends at regional and global scales. Here, we use the ensemble empirical mode decomposition method (EEMD) to investigate runoff oscillations at different time scales and its response to climatic fluctuations in the middle of the Yarlung Zangbo River Basin (MYZRB) over the period . In the study region, results revealed that the runoff presented an overall nonlinear and nonstationary decreasing-increasing alternative trend with weak quasi-three-year and unobvious quasi-five-year cycles at the inter-annual scale, while, significance was discovered with quasi-12-year and quasi-46-year cycles at the inter-decadal scale. Variance contribution rates of the hydrological components suggested that the inter-annual oscillations played an essential role in the runoff variations in the MYZRB. According to the reconstructed inter-decadal runoff series, the runoff may keep declining in future. For the response of runoff to climate change, overall, the runoff had a positive correlation with precipitation and a negative correlation with extreme temperature. But the runoff did not show obvious correlation with mean temperature. Furthermore, from a temporal scale point of view, the inter-annual runoff showed significant response to the inter-annual precipitation. The inter-decadal runoff strongly responded to the inter-annual extreme temperature. These findings will help us understand the hydro-climatic intrinsic mechanism in the MYZRB and develop better water resources management to account for climate change impact.

Hydro-Meteorological Trends in the Yarlung Zangbo River Basin and Possible Associations with Large-Scale Circulation

“…Few human activities have been found in the YLZR basin and the natural runoff play an important role in its performance of providing water resources. The runoff inter-annual oscillations and its response to climatic fluctuations in the middle of the YLZR basin played an essential role in the runoff variations in the middle of the YLZR basin, and the runoff had a positive correlation with precipitation [30]. The main periods of runoff in the YLZR basin were about 40-70 and 80-128 months at intermediate and long-term scales, respectively [31].…”

“…Although studies for investigating the hydro-meteorological changes over the YLZR basin are available in the literature, few can be found for exploring the trends of the runoff associated with large-scale circulation. Changes in regional air temperature have considerable impacts on the snow cover and glaciers within the YLZR basin [32][33][34], which in turn affects the water resources of the basin [30]. In recent decades, the air temperature within the YLZR basin has shown a significant trend of increase [16].…”

Climate Changes and Associated Multiscale Impacts on Watershed Discharge over the Upper Reach of Yarlung Zangbo River Basin, China

“…Analysis Product and China daily gridded Temperature Analysis Product (CPAP and CTAP, respectively) are produced and routinely calibrated by NMIC and CMA, based on the observations from approximately 2472 national meteorological stations [13,20]. All the observations used in CTAP and CPAP have undergone a rigorous quality control (QC) check in three steps of extrema detection, internal consistency check, and spatial consistency check before being interpolated [12,21]. Both CTAP and CPAP consist of daily observations for precipitation and temperature with a 0.25°× 0.25°grid size.…”

“…e CPAP has been widely used as a reference to validate the accuracy of satellite-based precipitation products [22][23][24][25] and as a reference to investigate climate change [13,26]. Also, it was pointed out that the CTAPs, including maximum (Tmax), minimum (Tmin), and mean (Tmean) temperatures, have enough accuracy for analyzing climate change at the basin scale [12,13]. e CPAP and CTAP during 1961-2009 were selected to obtain annual total precipitation and temperature for each grid in this study.…”

“…As a typical mountainous watershed with water supply mainly from the Chemayungdung Glacier in the northern slope of the Himalayas, the YZRB is well known as the highest river basin in the world, with the mean elevation exceeding 4600 m a.s.l. [11,12]. e complex topography with high elevation of the YZRB, especially in the upper reach of the basin, has hampered the settlement of hydrometric gauges and stations [13].…”