AbstractFor the first time, by analyzing the spatial variations and diurnal dynamics of the water regime of the small river of the Anadyr Lowland, the main sources were studied and the dynamics of the river discharge feeding were estimated. In the midstream and downstream reaches of rivers, the stability of the water regime is ensured by thawed waters of seasonal ice; in mountain rivers’ headwaters, by condensation waters. Suprapermafrost water reserves from the thawing of the upper 30-cm layer vary in low-lying tundra within 80–220 mm. The contribution of meltwater from seasonal ice of the active layer to river discharge at the beginning of the warm season is ≥60% of the total discharge. The water regime of tundra rivers during this period is distinguished by daily cycles in which the water level and temperature are in an antiphase. The modulus of the discharge of condensation waters in the river head from the catchment area, composed of detrital ground, in July–August varies within 15–50 L/km2 s. The condensation waters are characterized by daily in-phase fluctuations in the level and temperature of water in brooks with an amplitude of the temperature of the atmospheric and in-ground air of 16°C. Summer atmospheric precipitation determines the discharge regime of tundra rivers with their abundant fallout (30–60 mm) and complete saturation of the active layer with moisture in August–September. In June, atmospheric precipitation up to 14 mm is completely spent for the evaporation and vegetation of plants and does not affect the river discharge.