Temporal variability of catchment storage-discharge characteristics and their driving mechanisms in cold region

The catchment storage-discharge characteristics (CSDC) are usually the highly sensitive parameters in hydrology model and fundamentally decide the baseflow simulation performance. With dramatic climate change, several recent studies had found significant trend of the power-law parameter of CSDC (b₀) in cold region. However, studies about the temporal variability of b₀ and its driving mechanism in cold region are less consistence because of differences in study area and time scale. In this study, the b₀ was firstly calculated from daily recession event in 315 cold catchments, after which the time-varying rule of b₀ and its driving mechanism was investigated at events, warm period and decades scales. The results show that the set of calculated b₀ have a median of 2.1 around all study catchments and are great different between flow recession events in a specific catchment with the median of its variance in all study catchments is equal to 2.3. Moreover, the b₀ increased within warm period in most (78%) cold catchments and had also an increase on the decades scale in 63% cold catchments, stating a significant time-varying characteristic. Correlation analysis presents that permafrost extent degradation, increases in both precipitation (P) and terrestrial water storage (TWS) play the positive roles in b₀, while increasing PET play the negative role on the contrary. On the events scale, potential evaporation (PET) is the main control of the b₀, followed by the permafrost extent, while P and TWS take a slightly positive effect. During the warm period, permafrost thawing overtakes PET as the main control of the b₀, followed by the PET, and the effect of P and TWS can be not negligible. On the decade scale, climate change (i.e, climate warming and wetting) caused permafrost degradation and increases in both P and TWS, which has further increased the b₀. These results are of great significance for improving the understanding of the catchment storage-discharge process, and highlight that traditional hydrology modelling with constant CSDC could result in systematic bias in baseflow simulation and prediction in cold region.