THE EFFECTS OF LAND-SURFACE HETEROGENEITIES ON THE HYDROLOGICAL CYCLE

The effects of small-scale spatial heterogeneities of soil, land use a nd vegetation on area-averaged components of the water balance of a ri ver basin are investigated. Different parameterizations of these effec ts are tested on the base of the distributed model of the hydrological cycle. The model includes a description of the vertical moisture tran sfer in the ''soil-vegetation-atmosphere'' system, the overland flow a nd the river channel system routing. The heterogeneities are divided i nto deterministic (mosaic) and stochastic components. To parameterize stochastic components the procedures based on probability distribution s of basin constants and the theory of fractals were used. The case st udy is carried out for the Seim River basin located in the central par t of the forest-steppe zone of Russia (catchment area about 7500 km(2) ).