Flow composition mediates the sensitivity to air temperature of streams in a Qinghai-Tibetan watershed

The impact of runoff components on the sensitivity of stream temperature to air temperature remains unclear in alpine watersheds. Here we developed a distributed watershed model to capture essential hydrological-thermal processes in alpine watersheds and quantify runoff components impact in a Qinghai-Tibetan watershed. Between 1990 and 2023, runoff accounted for 56.5% of the stream temperature, with rainfall being the main contributor, followed by glacier melt, groundwater, and snowmelt. Under a high-emission scenario, the contribution of groundwater to stream temperature is projected to increase from 7.4% to 17.8% by 2100, accompanied by a declining contribution from air temperature, leading to spring and winter warming. Although the contribution of rainfall is projected to decrease from 36.0% to 28.0%, increased precipitation will lead to higher stream temperatures in summer. In source regions, the contribution of glacier melt, estimated at 15.0%, mitigates summer warming, whereas the impact of snowmelt remains limited. Runoff contributes almost equally to stream temperature as air temperature in a Qinghai-Tibetan watershed, and under high-emission scenarios the influence of groundwater is projected to increase, leading to spring and winter warming, according to hydrological–thermal modeling