Author(s): Khishigbat Batdelger; Ayurzana Badarch; Tomasz Kolerski; Nasanbayar Narantsogt
Linked Author(s): Ayurzana Badarch, Tomasz Kolerski
Keywords: River ice; Flow–ice interaction; Winter severity; Cold-region hydrology; Eg-Selenge River system
Abstract: Understanding river ice under natural flow conditions is essential for interpreting cold-region hydrology and establishing reference conditions for river management and climate-change assessment. This study presents an observation-based analysis of ice thickness dynamics and winter flow regimes in the Eg–Selenge river system in northern Mongolia using long-term records from the Eg-Khantai, Selenge-Khutag-Undur, and Selenge-Khyalganat gauging stations together with meteorological data. The study combines multi-station ice-thickness observations, winter discharge analysis, winter severity assessment, and cumulative freezing-degree analysis to define the natural ice-thickness regime of a natural river system. Ice phenomena generally begin in October, stable ice cover forms in November, and breakup occurs in April. Ice thickness follows a repeatable three-phase seasonal pattern of rapid early-winter growth, slower mid-winter thickening, and late-winter decay. Eg-Khantai sustains the thickest ice cover, whereas Selenge-Khutag-Undur shows the strongest long-term reduction in maximum thickness, with declines of about 17 cm and 24 cm, respectively, between historical and recent periods. Winter flow decreases sharply during freeze-up, reaches minimum values in January–February, and begins to recover in March while the river remains ice covered. At Selenge-Khyalganat, the same seasonal pattern is preserved at larger magnitude, reflecting the combined winter flow signals of the Eg and upper Selenge branches. Winter severity mainly affects ice formation and early thickening, whereas cumulative freezing degree-days provide the strongest control on seasonal ice growth up to about mid-March. These results establish a quantitative natural baseline for future assessment of climatic change and river management impacts on river ice processes.
Year: 2026