ABSTRACT

According to simulations, permafrost area in the Tienshan Mountains has decreased by about 1.73 × 10⁴ km² (or 20.91%) from the 1960s to the 2000s, and the freeze state of seasonally frozen ground (SFG) exhibited delaying freeze, advancing thaw, shortening freeze days and shallowing freeze depth. River discharge has changed largely, especially for winter and minimum monthly discharge. The rivers with low catchment permafrost coverage tended to have the highest 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). Gradually 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 a result of frozen ground degradation, summer precipitation may strengthen the influences on low flow.