БЕЗДОЩОВІ ПЕРІОДИ В СУЧАСНИХ КЛІМАТИЧНИХ УМОВАХ ЯК ФАКТОР МЕЖЕННОГО СТОКУ НА РІЧКАХ ПІВДНЯ УКРАЇНИ

Abstract

The concept of non-rainfall periods is used to assess the climatic conditions of agriculture and water management for relatively short periods of time. Non-rainfall periods are a criterion for dryness because they characterize the length of the period without effective precipitation. Now, the period of modern climate change is of scientific and practical interest, as the study of the whole process as a whole, and changes that occur in individual climatic characteristics, such as the formation and duration of non-rainfall periods. The magnitude of rainfall, the intensity of their precipitation, or their absence determine in essence the presence and duration of low flow periods on rivers. Particularly relevant is the study of factors in the formation of runoff of low flow periods in the South of Ukraine, which can also be characterized as a zone of insufficient water. The main source of filling for rivers in the low-water period of the year is primarily groundwater runoff, as well as rainfall, which enters the channel network through their infiltration into groundwater. Therefore, long non-rainy periods can lead to a decrease in the underground supply of rivers, and sometimes to their drying up. Based on the definition of the non-rainfall period, in the study, such periods were determined according to regular observations of precipitation for the warm season (April-October) 1991-2019 at 41 meteorological stations in southern Ukraine. To study the impact of the duration of non-rainfall periods on the groundwater regime used data from the directory “Groundwater Status” for 2021. As a result of the analysis of the initial data, information was obtained on the recurrence and total duration of non-rainfall periods in the study area. In the South of the country in the period under review, the number of such periods ranged from 1 to 10 per season. It should be noted that in some years no non-rainfall periods were detected at some stations. The maximum values of the total number of days in non-rainfall periods reached 161 days in 2018 in Rozdilna (Odesa region), 155 days in Nova Kakhovka (2011), 154 days in the Black Sea and Henichesk in 2012, 153 days in Odesa, Chernomorsk and Bekhtery (2019), 150 days in Belgorod-Dniester (1992). Synoptic analysis of weather conditions in 2015 and 2016 showed that the formation of the longest non-rainfall periods due to the predominance of anticyclonic weather for a month or more, resulting in September in some areas turned out to be the driest for the whole period of observations. Analysis of the dynamics of groundwater levels showed natural tendencies to reduce their level with increasing duration of non-rainfall periods, which may adversely affect the supply of rivers in the dry period in modern climatic conditions