The Boundary of the Sufficient Soil Moisture Zone in Ukraine is Shifting North

In Ukraine, there is a noticeable increase in the frequency of prolonged but ineffective rains, where the majority of precipitation falls within one or two days, as well as a reduction in the area with sufficient soil moisture. At the same time, the boundary of this zone is gradually shifting northward across the country.

This is reported by AgroReview

Dynamics of Moisture over 23 Years

According to research by agricultural science candidate Andriy Fedorенко from the Institute of Plant Protection of NAAS, long-term changes in the hydrothermal coefficient (HTC) have been analyzed. According to data from the Ukrainian Hydrometeorological Center, the average long-term value of HTC for the Steppe should be 0.9, but over the past 23 years, this figure has decreased to 0.82. For the Forest-Steppe, the normative HTC is 1.3, which corresponds to the zone of sufficient moisture; however, during this period, it has actually decreased to 1.12, turning the zone into one with insufficient moisture. In Polissya, the HTC, while remaining at the level of “wet” conditions (1.42), has also decreased by 0.08 compared to the average long-term value.

“According to the Ukrainian Hydrometeorological Center, the average long-term value of HTC for the Steppe zone should be 0.9, but according to my research, over the past 23 years, this figure has decreased to 0.82 (Table 2). For the Forest-Steppe, the normative HTC is stated as 1.3, which corresponds to the characteristic of the ‘sufficient moisture’ zone; however, during the analyzed period, this figure is 1.12, which already indicates a ‘deficient moisture’ zone. In Polissya, the HTC of 1.42 is still within the range of ‘wet’ conditions, but it has still decreased somewhat (by 0.08) compared to the corresponding average long-term value,” the scientist notes.

Climate Changes and the Spatial Shift of the Moisture Zone

The average HTC value for all of Ukraine should be 1.3; however, from 2002 to 2024, it has decreased to 1.1. A particularly significant reduction is observed during the active growing season (April-September), when the HTC decreases faster than the annual average. In the Steppe, this difference during the growing season is 0.17, which is more than double the annual difference (0.08). For the Forest-Steppe, this figure is –10, and for Polissya – 5.

The HTC during the active growing season has increased by an average of 0.26 across Ukraine, which is 0.06 more than the annual increase. Between 2002 and 2024, the climate across the entire country, as well as in each natural-climatic zone, has become drier. The lowest HTC values (0.8) were recorded in 2009, 2015, and 2018, which is 0.43 lower than the average long-term value (1.23). The HTC was around 0.9 in 2003, 2011, 2017, and 2024. At the same time, the wettest years – 2004 (HTC 1.5), 2005 (1.46), and 2010 (1.4) – occurred at the beginning of the analyzed period, but even then, a downward trend was evident.

HTC values that exceeded the average long-term value (1.23) were observed in 2014, 2021, and 2022 (1.3). To track changes in precipitation distribution, the average HTC values over the last 5 years (2019–2024) for each region of Ukraine were analyzed and mapped. A comparison with data from 1986–2005 clearly indicates a reduction in the zone of sufficient soil moisture, the boundary of which is gradually moving in a northwestern direction.