UNFROZEN WATER CONTENT OF SOILS IN RIVER WATERSHEDS AT NEGATIVE TEMPERATURES

I. L. Kalyuzhnyi and S. A. Lavrov

The unfrozen water content of seasonally freezing soils in river watersheds considerably influences soil water suction during spring period. Its neglect leads to errors in forecasting snowmelt runoff losses. It is found that unfrozen water content depends not only on temperature, but also on soil type and its mechanical composition. It is shown experimentally and justified theoretically that there is a relation between unfrozen water content and total soil moisture content. The curve of this relation has a maximum. In loam, the difference between maximum and minimum values reaches 3% of volume. A formula is obtained for determining a dependence of unfrozen water content on soil temperature at a fixed potential of soil moisture equal to —1500 and —5000 J/kg.