DETERMINATION OF WATER DEMAND FOR IRRIGATION BASED ON THE CLIMATIC WATER BALANCE IN THE EASTERN FOREST STEPPE OF UKRAINE IN VIEW OF THE NATURAL WATER SUPPLY

The results of the research show that even today crop cultivation in the entire territory of the steppe and in a large part of the forest-steppe zone is carried out in conditions of a significant deficit of the climatic water balance, which necessitates a significant expansion of irrigation application as a mandatory element of the of highly efficient and sustainable cultivation technologies of the most of crops. Therefore, without active measures to adapt agricultural production to climate change, which is accompanied by a significant increase in the frequency and duration of drought events and, accordingly, a shortage of moisture supply, the restoration and development of irrigation remains the main factor in increasing the productivity of field crops. The research was conducted in the Eastern Forest Steppe zone. For the assessment and analysis of climate change, raw meteorological data for 1961-2020 were used. The data source is the Global Climate Monitoring (GCM) system developed by the Climate Research Group of the University of Seville. According to the results of the assessment of the dynamics of the average annual air temperature for 1961-2020, it was established that over the past 30 years the temperature has risen on average by 1.2oC, and since 1987 the rate of its growth is 0.79oC over the decade, while the annual amount of precipitation remains practically unchanged. It was established that the potential evapotranspiration increased by 70 mm and is almost 850 mm per year. With such a difference between precipitation and potential evapotranspiration, the deficit of the annual climatic water balance reaches on average almost 300 mm over the last 30 years, against 247 mm in 1961-1990, and the tendency to its increase persists. Simulation modeling of the economic efficiency of irrigation based on preliminary results indicates the efficiency of its implementation, and especially restoration on areas with existing reclamation infrastructure.