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Hydraulic-fill dumps --ash dumps, tailings dams, sludge storage ponds, and others --operate continuously at any time of the year in various climatic regions of the Soviet Union. The most difficult period of operation of these structures is the winter, characterized by the effect of unfavorable climatic conditions: low negative air temperatures and strong wind, sharp temperature drops with thaws, and snow drifts. We note that in general it is not recommended to construct large hydraulic structures, for example, hydraulic-fill dams, under extreme meteorological conditions. In works [1][2][3], shedding light on problems of operating hydraulic-fill structures in winter, some basic problems were not reflected, particularly their thermal classification is absent.For the example of hydraulic ash disposal (HAD) systems of thermal power stations, we will examine problems of operating hydraulic-fill dumps in the winter and will classify them according to the thermal regime of the abovewater slope of the hydraulic fill and settling pond.In the winter operating period the temperature of the slurry arriving at the ash dump mainly depends on the type of ash collectors at the station: for wet collectors the slurry temperature is 12-20~ and for dry 3-5 ~ Individual channel flows of slurry form on the above-water slope, the area of which is considerably less than the area of the entire slope; the number of channels decreases with decrease of temperate. Various ice regimes are observed in the settling pond and on the above-water slope in the water slope in the winter: from the absence of an ice coating and ice to the complete covering by an ice coating and ice.Two main problems arise when operating dumps: effective storage of the material without loss of reliability of the structure and effective clarification of the water for reuse. A reduction of the size of the settling point and increase of the reliability of the dumps are prevented by the small settlement of the fine fractions of material on the above-water slope as a consequence of an increase of the slurry velocity with decrease of the number of channels; furthermore, the effectiveness of clarification in the settling pond decreases as consequence of the effect of the ice cover. In recommendations [2, 3] these characteristics of the winter regime of dumps are not taken into account, and therefore before determining the dimensions of the settling pond and capacity of the dump when calculating the water balance of the recirculated water supply systems it is necessary to determine the thermal state of the structure being planned.For a quantitative evaluation of the state of hydraulic-fill dumps during their winter operation we will use the heat-balance equation in a steady-state thermal regimewhere S 1 is the heat flow arriving with the slurry at the ash dump; S 2 is the heat leaving with the clarified water at the place of its entry into the sumps; S d = Sr f + Sr f + Se f + Sb f + Sp f is heat transfer of the flow on the above-water slope of the hydraulic fill; S p = SrP + S...

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