WATER-PHYSICAL PROPERTIES AND MODELING OF MOISTURE TRANSFER IN THE SOUTHERN CHERNOZEMS OF THE KANSK INTERMONTANE DEPRESSION (THE CHARYSH BASIN, NORTH-WEST ALTAI)
The physical and hydro-physical properties of the southern chernozems used for crops and pastures in the Kansk intermontane depression of the Altai (Charysh River, the 1st order tributary of the Ob River) were studied. The obtained water retention curves (WRCs) and hydraulic conductivity functions allow describing the vertical water transfer in unsaturated steppe soils as an outflow component of soil water balance. The water retention curves for the investigated soils were constructed based on semi-empirical methods. Using the pedotransfer functions from RETC 6.02 v.1.1 software, we determined the parameters of WRC approximation by van Genuchten function due to the data on soil density and granulometric composition (in line with the international classification). The WRCs were also constructed by means of soil-hydrological constants according to the Voronin's secants method. The WRCs for the southern chernozems of the Kansk steppe constructed by different methods show good convergence for low soil pressure and moisture. With soil drying up and reducing pressure of soil moisture, the WRC of more compacted B and C horizons are shifted to the right, i.e. to higher moisture values. This is due to the fact that the water retention capacity of dry soil depends on thin capillaries which are abundant in consolidated soils. A looser horizon Аp of the southern chernozems used as tilled lands (under crops) keeps moisture better at high moisture values. It is found that the hydraulic conductivity of Bk horizon of the southern chernozems under the pasture is higher than that of tilled soil. Therefore, a vertical downward flow of moisture will be better pronounced between A and B horizons of the southern chernozems under pasture than under crops (in tilled soil). Obviously, within the tilled layer a lateral subsurface runoff will be clearly marked.