Application of the Operator Model for Determination of Maximum Modulus of Spring and Rain Floods at the Rivers within Vistula River Basin inside Ukraine

Purpose. To substantiate the calculated characteristics of the slope influx and channel runoff, as well as to create a modern methodological basis for rationing the characteristics of the maximum runoff of spring and rain floods in the Vistula River basin within Ukraine. Methods. For calculating the maximum runoff of spring and rain floods, statistical processing of data series was performed according to the method of moments and the maximum likelihood method. The three-parametric gamma distribution was used to calculate the runoff layers and water discharges with a rare probability of exceeding. An operator model developed by E.D. Gopchenko (2001) and modified by V.A. Ovcharuk (2017) was used as a calculation to determine the characteristics of the maximum river runoff. To calculate the duration of the slope influx, a complex method was used using the software complex "Caguar", developed at the Department of Land Hydrology of OSENU. Results. The standard statistical characteristics of the time series of the maximum runoff of spring and rain floods are determined, they were used in further calculations to determine the maximum water runoff and runoff layers with a rare probability of exceeding. The paper substantiates and generalizes on the territory all parameters of the basic operator model of maximum runoff formation: coefficients of time non-uniformity of slope influx and duration of slope influx are determined, transformation function is calculated and maximum modules of slope influx for spring and rain floods are determined. Most of the calculated parameters are generalized by territory using GIS or calculation equations with the minimum amount of required input data. Conclusions. As a result of the study, a regional methodology was developed to determine the maximum runoff of spring and rain floods on the rivers of the Vistula River basin. In contrast to previous developments by domestic authors, the advantage is that the use of the operator model allows the use of a single formula, regardless of the genesis of the maximum runoff and catchment area. The obtained results of the research can be used in the planning of hydraulic engineering construction and flood control measures in the Vistula River basin within Ukraine in order to minimize losses and protect the population from the dangerous effects of water. The proposed model can be used for other areas