In the vertical structure of the river basin, the dominant formation is the soil. Conditions for the transformation of water supply to the surface of the basin are determined by the ability of the soil to give or, contrarily, retain a significant proportion of precipitation. The soil column in the process of formation of the flood hydrograph performs the functions of moisture transfer by two opposite signs of the vertical component: filtration and evaporation. The laws of infiltration were considered by us in the previous section, where it was found that the leading parameter of the infiltration process in addition to the intensity of rain is the filtration coefficient. There are many methods for determining evaporation from the soil, such as the methods developed by Konstantinova, Polyakova and Kuzina. We shall consider two methods for the sake of an example. The first one is an equation to determine evaporation by M.I. Budiko edited by Marchenko: bE y W bE y P K M Y I W h k 1 2 (1 / 2 ) 0 0  , (1) where k W and h W – are initial and final reserves of moisture in the root layer of the soil, b – is a biological coefficient, which depends on the phase of plant development; 0 E - evaporation; y – the productive value of the lowest moisture content; K – groundwater recharge; P – precipitation; M – deficiency of soil moisture to a condition of saturation of productive moisture; Y – surface runoff; I – infiltration beyond the root layer of the soil. All values (except b) are given in millimetres. The calculation according to equation (1) is carried out at time intervals, which are taken equal to the decade, the value h W for this decade is taken equal to the value for k W of the previous one. The second method is quite simple in structure. It is the method of A. Budagovsky. It was slightly modified by Y.B. Vinogradov based on Dalton's law. dE s  (2) as: [ ] m в E  k W W (3) where E – evaporation from the soil, k – turbulent diffusion coefficient of humidity, m W – maximum soil moisture, в W – real humidity. exp( / ) ~ 0 m W W E W (4) Evaporation from the soil surface at any time is equal to the sum of all water losses in all soil layers. For each of the latter, there is an equation: exp( /( ) ) ~ i i i 0 m i W W k E W (5) The problem of evaporation calculation is the assessment of evaporation. Here we can use the known correlation: E xcosdt 0 , (6) where d – the average deficit of humidity for the estimated time interval. The value of the coefficient x is within (0,3-0,6)10-3 m/(mbars) depending on the type of surface. In fact, the coefficient K is not a constant, it is different for different layers of soil and depends on the amount of moisture, especially in the subsurface layer. It is also seen that the stronger the layer, the more moisture in it and the higher the evaporation rate.