Abstract

According to the simulations, permafrost area in the Tienshan Mountains has decreased about 1.73 × 10⁴ km² (or 20.91 %) from 1960s to 2000s, and the freeze state of seasonally frozen ground (SFG) exhibited the delaying freeze, advancing thaw, shortening freeze days and shallowing freeze depth. The river discharge has changed commonly, especially for winter and minimum monthly discharge. The rivers with low catchment permafrost coverage tended to have the high increasing rates in winter discharge, minimum monthly discharge, winter discharge ratio (proportion of winter discharge contribution to total annual flow) and minimum monthly discharge ratio (proportion of minimum monthly discharge contribution to total annual flow). Gradual increasing correlations of maximum seasonally frozen depth (SFD) with the hydrological variables may indicate that the response of river discharge to frozen ground change is a long-term process. Possibly caused by frozen ground degradation, summer precipitation may strengthen the influences on low flow.