Abstract
The accelerated climate warming in the Tibetan Plateau after 1997 has strong consequences in hydrology, geography, and social wellbeing. In hydrology, the change of streamflow as a result of changes of dynamic water storage originating from glacier melt and permafrost thawing in the warming climate directly affects the available water resources for societies of the most populated nations in the world. In this study, annual streamflow recession characteristics are analyzed using daily climate and hydrological data during 1980–2015 in the Yarlung-Zangpo River basin (YRB) of south Tibetan Plateau. The recession characteristics are examined in terms of dQ/dt = −aQb and the response/sensitivity of streamflow to changes of groundwater storage. Major results show that climate warming significantly increased the nonlinearity of the response (b) and decreased streamflow stability [log(a)] in most sub-basins of YRB. These changes of recession characteristics are attributed to opposite effects of increases of available water storage and recession timescale on the recession. Climate warming increased sub-basin water storage considerably by more recharge from accelerated glacier melting and permafrost thawing after 1997. Meanwhile, the enlarged storage lengthens recession timescales and thereby decreases the sensitivity of discharge to storage. In the recession period when the recharge diminished, increased evaporation under warmer temperatures acts as a competing process to reduce water storage and streamflow. While reservoir regulations in some basins helped reduce and even reverse some of these climate warming effects, this short-term remedy could only function before the solid water storage is exhausted when the climate warming continues.
Highlights
The warming rates of air temperature in high latitudes and high altitudes are greater than the rate of change of global average near surface air temperature (e.g., McBean et al, 2005; Pepin et al, 2015)
The wet trend is largest in YBJ, 220 as well as LS sub-basins, whereas the mean temperature of YBJ is lowest because most of its area is at high altitudes
coefficient of variation (CV) decreases towards the wetter downstream of Yarlung-Zangpo River basin (YRB), partially because of strengthening watershed regulation as the sub-basin areas increase and the dams are included in the area of the analysis
Summary
The warming rates of air temperature in high latitudes and high altitudes are greater than the rate of change of global average near surface air temperature (e.g., McBean et al, 2005; Pepin et al, 2015). The accelerated glacier melting and permafrost thawing have increased the soil active layer thickness (ALT) and 40 enlarged groundwater storage by allowing exchange of the surface water and groundwater (Xu et al, 2017; Forster et al, 2014; Ji et al, 2020) Such exchange further alters streamflow composition in arctic catchments (Chang et al 2008; Walvoord and Kurylyk, 2016; Bring et al, 2016) and the northeastern and southern Tibetan Plateau (TP) (Li et al, 2018; Wang et al, 2018; Yi et al, 2021). Climate warming has reduced the buffering effect of glacial and permafrost on streamflow, leading to catchment property change with shorter streamflow response time to precipitation in YRB (Wang et al, 2021) These changes must have affected streamflow recession characteristics.
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