Groundwater Rise Sustains the World's Largest Alpine Water System Under Global Warming

Shallow groundwater dynamics on the Qinghai-Xizang Plateau (QXP)-the "Asian water tower" supplying freshwater to billions downstream-remain poorly understood despite their critical role in buffering climate impacts. Integrating more than 8000 in-situ groundwater records with multi-source remote sensing data, we present the first high-resolution assessment of shallow groundwater across the QXP's non-permafrost plains. From 2000 to 2020, groundwater depth has been decreasing at a rate of 0.02 m year^{- 1}, adding approximately 31.44 Gt (Gigatons) of freshwater storage-directly countering the prevailing narrative of widespread water loss. By combining the maximum capillary rise height, this rise sustains ∼53 500 km² of alpine ecosystems and is closely linked to increasing NDVI in emerging groundwater-dependent vegetation. These results reveal the possibility of ecosystem regime shift under shrinking groundwater depth, highlighting the importance of groundwater dynamics in understanding alpine ecosystem changes. With an estimated 426.6 Gt of remaining storage capacity in the vadose zone, we identify managed underground reservoirs as a promising but still prospective opportunity for climate adaptation. Our findings reveal that the QXP's shallow aquifers function as a dynamic, growing freshwater reservoir, challenging surface-water-centric views of water-tower vulnerability and suggesting that current studies may underestimate the resilience plateau's water system to ongoing global warming.