Distinguishing the Relative Contribution of Environmental Factors to Runoff Change in the Headwaters of the Yangtze River

Abstract

The change in river flows at the basin scale reflects the combined influences of changes in various environmental factors associated with climatic and underlying surface properties. Distinguishing the relative contribution of each of these factors to runoff change is critical for sustainable water resource management, but it is also challenging. The headstream region of the Yangtze River, known as “China’s Water Tower”, has undergone a significant runoff change over the past decades. However, the relative contribution of environmental factors to runoff change is still unclear. Here, we designed a series of detrending experiments based on a grid-based hydrological model to quantify the combined influences of multiple environmental factors on runoff change and the relative contribution of an individual factor to runoff change. The results indicate that changes in climate and vegetation significantly increased water yield in the study basin over the past three decades, and the increase in water yield primarily came from the contribution from the upstream of the basin. On the basin scale, the change in precipitation dominated the runoff change that contributed up to 113.2% of the runoff change, followed by the wind speed change with a contribution rate of −15.1%. Other factors, including changes in temperature, relative humidity, sunshine duration (as a surrogate for net radiation), and albedo (as a surrogate for vegetation) had limited effects on runoff change, and the contribution rate of these factors to runoff change ranged from −5% to 5%. On spatial patterns, the influences of changes in some environmental factors on runoff changes were affected by elevation, particularly for temperature. The rising temperature had mixed effects on runoff change, which generally increased water yield at high altitudes of the basin but decreased water yield at low altitudes of the basin.

Inverse Trend in Runoff in the Source Regions of the Yangtze and Yellow Rivers under Changing Environments

“…Attribution analysis showed that other environmental factors contributed between −5% and 40%, and the contribution of this part comes from glaciers permafrost and human activities. The SRYZ has the highest concentration of glaciers and permafrost in China, accounting for 0.95% and 75% of the whole basin area, respectively [6]. In recent decades, the temperature in the SRYZ increased significantly, with an increase of 0.6 • C/10a, which was about four times of the global mean [48].…”

“…Climate change has had significant effect on the water cycle in the basin through factors such as precipitation, temperature, sunshine, wind speed, etc. [5,6], with precipitation being the crucial driving factor [7]. In addition, with rapid economic development, human activities are altering the ecological environment of a basin in the form of greenhouse gas emissions, land-use changes, water conservancy construction, and human water consumption, resulting in an increasingly significant effect on river runoff [8,9].…”

“…In addition, the simulation accuracy of the hydrological methods is also improved with the innovation and popularization of computer technology. However, the hydrological model contains many parameters [6], and the simulation results depend largely on various assumptions in the model, with a significant degree of uncertainty. In contrast, the Budyko-based elasticity method is based on the hydrothermal balance and has a solid physical basis [1,14].…”

Different Vegetation Information Inputs Significantly Affect the Evapotranspiration Simulations of the PT-JPL Model

“…However, the assumption of S = 0 may not hold, especially in small basins [53,73]. Small basins often have frequent water exchange with neighboring basins, and ignoring this part of the water may result in a large bias in ET estimation from the water balance method [74].…”

Spatiotemporal Variations of Meteorological Droughts and the Assessments of Agricultural Drought Risk in a Typical Agricultural Province of China

“…Increased drought frequency and intensity since 1995 is likely due to the effects of climate change. With global warming, the Earth's climate system becomes more unstable than ever before [44], causing drought events to become more frequent in many regions of the world [45][46][47].…”