Jökulhlaups in the Kunmalike River, southern Tien Shan mountains, China

Hydrological records of Kunmalike River in the southern Tien Shan show that jökulhlaups have occurred about once a year since 1956 from the glacier-dammed Lake Mertsbacher. The maximum peak discharge of the jökulhlaups is 1920 m3s−1and the maximum total volume is 3.275 × 108m3. The release mechanism of the glacier-dammed lake is not a mechanical failure of the glacier dam, but drainage of pressurized water through a subglacial tunnel which is enlarged due to melting by frictional heat in the flowing water and advective heat from the lake. There is no relationship between the size of the jökulhlaups and the mean summer air temperature. The seasonal flood peaks in Kunmalike River have become larger and the flood periods have been prolonged both in spring and winter because of the draining of the lake. Once a jökulhlaup has started, its discharge is forecast hour by hour by extrapolating the measured hydrograph as exponential curves.