Evaluation of Water Content in Soils of Žitný Ostrov from the Point of View of Its Exploitation for Biosphere

The lithospheric zone between the soil surface and the first ground water horizon, respectively the ground water table, has a character of three-phase system. It consists of solid phase having fine to rough disperse granularity. This creates a structure of porous environment with characters that can be physically determined. The water occurs in pores in different forms of state and its bond with solid phase. Its energetic bond is clearly quantified by means of moisture retention curve. The gas phase fills pores with the water up to the value of the full porosity, i.e. it fills the part of pores that is not saturated with water. Therefore, this lithospheric zone is called the soil aeration zone. The volume of water occurring in the soil aeration zone corresponds to the concentration of water in the framework of hydrological cycle components. This water serves as the water resource for the vegetation cover. The data used for calculation were particular soil types in the area, depth of ground water table, hydrolimits (wilting point, point of decreased availability, field water capacity) and aeration zone thickness. The water content in the soil aeration zone between hydrolimits field water capacity (FWC) and wilting point (WP) is the critical interval of water content for vegetation cover in a given locality. Water from this interval is available for the vegetation cover. This water has no properties of free water, and plants have to have a developed root system and such suction pressure, that is able to overcome the bond between water and soil. Calculated results were verified with the help of monitored water content. Both calculated and measured values of soil water content in the aeration zone show that the water content is affected by appurtenant soil type. The human activity in a landscape directly affects the dynamics of this water resource, either from quantitative or qualitative viewpoint. This affect is demonstrated by changes of the ground water regime, i.e. changes of ground water table and amplitude of its fluctuation. The paper brings results of water content evaluation in the soil aeration zone in the Žitný ostrov area.