Work

Runoff efficiency and seasonal redistribution under warming–wetting in the Pangu River basin: A snow-state-constrained assessment

Year: 2026

Type: article

Abstract: Study region The Pangu River basin is a data-scarce, high-latitude mountainous catchment in the northern Greater Khingan Mountains, Northeast China, where runoff is jointly shaped by seasonal snow, freeze-thaw processes, river ice, catchment storage-release, and limited direct human regulation. Study focus We examined annual runoff and seasonal release under warming-wetting using harmonized monthly runoff observations, a cold-region process-diagnostic model (PHY), and targeted tests of total-runoff residual, parameter, and snow-structure sensitivity. Diagnostic pathway allocation was treated as secondary sensitivity analysis. New hydrological insights for the region Within the snow-state-constrained reference model, historical runoff did not increase proportionally to wetting. Between 1961–1990 and 1995–2024, annual precipitation increased by 53.7 mm, whereas PHY annual runoff changed by only −3.0 mm and runoff efficiency declined from 0.265 to 0.228. April–June (AMJ) runoff showed a model-inferred directional decline of 4.8 mm, with a relative shift toward July–October (JASO); bootstrap intervals for AMJ runoff and seasonal-allocation contrasts included zero. In the PHY diagnostic decomposition, the snow-related spring-release index (SAI) declined from 0.312 to 0.278. Runoff directions persisted under local parameter and residual perturbations, and lower SAI persisted within the reference parameter ensemble. Removing ERA5-Land snow-state assimilation reversed the key historical directions. The efficiency contrast reflects a response conditioned by effective-forcing and numerical snow-state adjustments, not an identified fate of additional precipitation. Weaker snow-supported spring release is therefore a conditional model interpretation, not an established climatic mechanism.

Source: Journal of Hydrology Regional Studies

DOI: 10.1016/j.ejrh.2026.104124