Formation of Spring Overland Runoff on Agricultural Lands of the Forest-Steppe and Steppe Zones in European Russia

An analysis and integration of long-term experimental data has made it possible to formulate important theoretical and practical conclusions. The genesis of the process of flow formation is revealed and its theoretical justification is given. A pattern has been discovered, which implies that only three natural factors have a significant impact on spring overland runoff: snow reserves, freezing, and the degree of soil moisture. At certain (limiting) levels (when freezing depth is less than 50 cm, moisture reserves in the soil layer of 0-50 cm are less than 70-120 mm in the zones, and snow reserves are less than the volume of free pores in the 0-30 cm soil layer), runoff is not formed. If the indicators of the levels of each of these factors are higher than the limiting ones, then the runoff is necessarily formed, and its size (layer) does not depend on the depth of freezing, as absorption occurs only in a layer from 3 to 30 cm (varying by zones and years), because a waterproof ice screen is formed in it, below which snow water does not arrive. The amount of runoff depends on the free porosity in this layer of soil and snow reserves. Free porosity, in turn, depends on the degree of soil moisture. The amount of runoff during deep freezing of the soil depends on its humidity and snow reserves before snowmelt. These factors are the main ones in the emergence of runoff formation conditions. The main role is played by soil moisture. Snow reserves play a passive role in the formation of runoff. Its value depends on snow reserves, but they do not directly affect water absorption; that is, part of the snow water drains after filling the free pores, and the more it is in the snow, the more it will drain. Knowledge of the genesis of the interaction of meltwater with frozen soil allows us to approach the prediction of the overland runoff of meltwater on a genetic basis.