Territorial forecasting of the dry weather flow of the rivers of the Southern Bug river basin
Authors:   Odessa State Environmental University, Blaha Anastasia , Shakirzanova Zhannetta 
Published: December 2023

Dry weather flow is forms due to the depletion of both groundwater reserves and channel reserves, which still remain in the river network, lakes and swamps after the termination of the supply of surface thaw-rainwater from spring irrigation. Forecasts of the river boundary flow in the summer, autumn and winter period are used in the development of monthly and decadal plans for the operation of large reservoirs, in the planning of navigation, energy production of hydroelectric power plants on rivers, which should ensure reliable, uninterrupted operation of economic facilities, as well as in forecasts of low water in rivers. The object of the research is the rivers of the Southern Bug river basin. The summer and winter dry weather flow on the rivers of the Southern Bug river basin is characterized by stability, low water and considerable duration; autumn rises are observed after torrential rains. Sometimes the dry weather flow is broken by small rain floods. The purpose of this work is to develop a methodology for territorial forecasting of the dry weather flow of rivers in the Southern Bug river basin and to evaluate its effectiveness, a cartographic presentation of the predicted values of the dry weather flow and to determine the probability of their occurrence in a multi-year period. The basis of the forecast of low water flows in the dry weather flow period of rivers in the basin of the Southern Bug River is the solution of the water balance equation in the form of dependencies generalized for a number of the water gauge station. According to the data on water flow (runoff modules) on the date of the forecast release and averages for the decade, regional dependencies were constructed for each month of the season of low water flow of rivers separately. The methodology of territorial short-term forecasts of the average decadal flow of water of the dry weather flow summer, autumn and winter runoff of rivers in the basin of the Southern Bug River is evaluated as satisfactory - the interval of the criteria of quality and efficiency of the methodology is 0.68-0.84, and the short-term forecasts evaluation is quite high - Р % varies from 70% to 94%, with the number of members of the series exceeding 500 points. In the prognostic method of territorial short-term forecasts of the dry weather flow of rivers in the basin of the Southern Bug River, it is proposed to establish the certainty or probability of exceeding (probability of occurrence of) forecast values (P%), which is especially important for rivers that have not been studied in terms of hydrology. In order to determine the reliability of forecast values of average decadal water flows of the summer, autumn and winter dry weather flow, the empirical distribution of the average monthly runoff modules in the specified boundary seasons in river basins in the basin of the Southern Bug River was established. Map-schemes of distribution on the territory of forecast values of average decadal water consumption and their probable values were constructed using the program Surface Mapping System Surfer Version 11.6.1159. The map schemes are built on the date of the release of the forecast make it possible to carry out spatial monitoring of the dry weather flow of rivers and to issue forecasts of water runoff during this period in a specific point of the territory, even for those rivers for which there is no monitoring of the runoff.