This paper presents a variant of the informationmodeling system for short-term forecasting of floods in the Upper Ob basin. A period of spring flood is considered. Hydrological regime of the river Ob and its major tributaries is calculated on the basis of one-dimensional nonstationary model (a “shallow water” model) for a system of channels. The data from gauging stations are used as boundary conditions. In the gauging — free zone, the water inflow to the river network is defined by the model for the snowmelt runoff formation that is based on a vertical one-dimensional nonstationary submodel for heat and mass transfer in the snow. The latter allows us to calculate snowmelt and water loss from the snow cover. Along with the snowmelt model, we use a simple model for the runoff transformation consisting of 2 components, i. e. surface and soil. The surface runoff is calculated by the catchment area with regard to the “lag time” concept. The catchment area of river Losikha that is a part of the Upper Ob basin is calculated using the model for snowmelt runoff formation. The results of calculations of spring flood transformation in the Ob at the site Biysk- Kamen-on-Ob are presented. The calculated and field data on water discharge demonstrate a satisfactory correlation.