Variation in the hydrological cycle in the Three-River Headwaters Region based on multi-source data

Abstract

The hydrological processes in the Three-River Headwaters Region (TRHR), which is located in the Qinghai-Tibetan Plateau and includes the Yangtze River Headwater Region (YARHR), the Yellow River Headwater Region (YERHR), and the Lantsang River Headwater Region (LARHR), have changed under climate warming. Based on multi-source data, the spatial and temporal changes in precipitation, evapotranspiration, soil water storage, glacier melt, snowmelt and runoff in the Three-River Headwaters Region from 1982 to 2014 were comprehensively analysed. The annual precipitation data for the Three-River Headwaters Region from ERA5-Land, the Climatic Research Unit, the China Meteorological Forcing Dataset and the Global Land Data Assimilation System (GLDAS) all showed an increasing trend; the annual evapotranspiration data from ERA5-Land, Global Land Data Assimilation System, Global Land Evaporation Amsterdam Model (GLEAM) and Terrestrial Evapotranspiration Dataset across China (TEDC) all showed an increasing trend; and the annual soil water storage data from ERA5-Land, Global Land Data Assimilation System and Global Land Evaporation Amsterdam Model all showed an increasing trend. The annual snowmelt data from ERA5-Land, Global Land Data Assimilation System and SMT-Y datasets all showed a decreasing trend. The annual glacier melt increased in the Yangtze River Headwater Region and Yellow River Headwater Region and decreased in the Lantsang River Headwater Region. The increases in precipitation, evapotranspiration, soil water content and glacial melt, and the decreases in snowfall and snowmelt indicate an accelerated hydrological cycle in the Three-River Headwaters Region over the 1982 to 2014 period. The significant increase in precipitation is the main reason for the significant increase in runoff in the Yangtze River Headwater Region. The increase in precipitation in the Yellow River Headwater Region was less than the sum of the increase in evapotranspiration and soil water storage, resulting in a decreasing trend of runoff in the Yellow River Headwater Region. The increase in precipitation in the Lantsang River Headwater Region was slightly larger than the sum of that in evapotranspiration and soil water storage, and there was an insignificant increase in the runoff in the Lantsang River Headwater Region.

Response of runoff and its components to climate change and its future trend in the source region of the Yangtze River

“…The Yangtze River source changes from wet to dry from southeast to northwest, and it is a semi-humid and semi-arid cold plateau ecosystem. The average annual precipitation is 221.5-515.1 mm, concentrated from May-September, which accounts for 75% of the annual precipitation on average (Yao et al, 2014). The Yangtze River source, which has a low oxygen content, harsh living environment, many uninhabited areas and low human impact (Wu et al, 2021), is an ideal zone for studying the response of hydrological processes to climate change.…”

“…Overall, the warming rate of the Tibetan Plateau doubled the global average level during the same period, and precipitation has also increased in recent decades (Xu et al, 2008; Yao, 2019). The glacier areas in the Yangtze River source in 2019 decreased by 39.4% compared with those in the 1970s (Yang et al, 2022), and the snowmelt period started earlier and ended later in the Tuotuo River in the Yangtze River source during 1960–2012 (Wang et al, 2015). Thus, changes in runoff and its components due to climate change in the Yangtze River source have become indisputable, and exploring the characteristics of runoff changes is important for the protection of water resources and ecological environment in the area.…”