Impact of climate change and permafrost degradation on runoff components in Hailar River Basin

Abstract

[Objective] Investigating the impact of climate change and permafrost degradation on runoff components in the Hailar River Basin is important for revealing hydrological evolution mechanisms and optimizing adaptive water resource management strategies in river basins of cold regions. [Methods] Using hydrological, meteorological, and permafrost observation data from 1980 to 2012, runoff components were partitioned using the digital filtering method. Permafrost variation characteristics were simulated using the Stefan model, and the relative contributions of precipitation, air temperature, permafrost depth, and vegetation cover to variations in runoff components were analyzed using the grey relational analysis method. [Results] The result showed that:(1) runoff in the river basin decreased significantly during the study period. The reduction rate at each station ranged from 15.5 mm·(10a)^-1 to 43.6 mm·(10 a)^-1, and baseflow accounted for over 70% of total runoff.(2) The Stefan model performed well in simulating the annual maximum frozen depth in the river basin. The maximum frozen depth showed a significant decreasing trend at a rate of 8.8~11.2 cm·(10 a)^-1.(3) The grey relational analysis result revealed that cold-season runoff had the highest correlation degree with permafrost, ranging from 0.78 to 0.83, while warm-season runoff had the highest correlation degree with vegetation coverage, ranging from 0.79 to 0.84. Air temperature showed a relatively low correlation degree at all stations, ranging from 0.60 to 0.69. [Conclusion] The result indicate that:(1) runoff and its components in the river basin exhibit a significant declining trend during the study period, with baseflow playing a dominant role in the changes in total runoff.(2) The Stefan model is applicable in simulating the annual maximum frozen depth in the river basin. Overall, permafrost degradation across the river basin is severe and exhibits significant spatial heterogeneity.(3) Cold-season runoff is primarily affected by permafrost degradation, while warm-season runoff is mainly controlled by vegetation cover, showing pronounced seasonal differences. Air temperature affects runoff indirectly by influencing permafrost thaw and vegetation growth.

Keywords

climate change / permafrost degradation / runoff / baseflow / Hailar River Basin / precipitation / digital filtering method / hydrological evolution mechanisms in cold regions