Delineating the hydrological processes and hydraulic connectivities under permafrost degradation on Northeastern Qinghai-Tibet Plateau, China

•The recharge ratios of three source waters to stream were quantitatively estimated.•The melting ground ice contributes substantial (13.2%–16.7%) input to stream water.•The near-surface ground ice exhibited different formation mechanism and source water.•Seasonal hydrological variations and hydraulic connections were conceptually modeled.