SYSTEM-ANALYTICAL MODELLING: 1. DEVELOPMENT OF REGIONAL MODELS FOR MOUNTAIN RIVER RUNOFF

The method of system-analytical modeling of complex natural systems is pro- posed to construct the regional simulation models of mountain river runoff. Using 34 mid-size and small rivers of the Altai-Sayan mountain country as a regional case study, a universal model of seasonal and long-term dynamics of the runoff was developed with good perfor- mance. To calculate the seasonal runoff, four hydrological periods were specified: winter low water, spring-summer flood, summer low water, and autumn low water. In the model, the hydrological regime of river basins is divided into 13 standard types that correspond to the selected groups of geosystems (landscapes). Each type of regime depends on six input fac- tors (precipitation and air temperature for the previous and current seasons, the area and elevation of landscapes) and is characterized by three parameters at the most for each sea- son. The proposed hydrological model deals with spatially generalized monthly dynamics of air temperature and precipitation expressed in percent of specified long-term mean values. Therefore, it can be applied for any river basin of the country even under the lack of meteo- rological information. It also uses GIS information on the relief and landscape structures of river basins. A well-behaved version of RMSE-Standard deviation Ratio (RSR) is applied to assess the model adequacy.