FROM THE HISTORY OF MODERN RESEARCH OF GEO-ECOLOGICAL PROBLEMS OF SMALL RIVERS OF WESTERN PODILLIA

Systematization of the authors' research and publications on the river-basin systems of small rivers of Western Podillia has been carried out. Three main stages are distinguished. The analyzed basic scientific works of these stages proved the expansion of the spectrum of geoecological studies of small rivers by representatives of the Lviv Scientific School under the patronage of Prof. I. Kovalchuk. At the end of the first stage (2005, 2007, 2010, such studies were carried out by representatives of the Ternopil Scientific Center under the leadership of Prof. L. Tsaryk. The study of the geoecological problems of small rivers reached special relevance in the middle of the second stage with the study of the natural resource potential in river basins (natural recreational, environmental protection, integral resources in the dissertation studies of S. Novytska, O. Greskiv, I. Vitenko, L. Babiuk. During this period, four candidate theses on this issue, a number of bachelor's and master's theses (O. Burtak, V. Tsaryk) were defended ).At the third stage, the activity of expeditionary research in the basins of the rivers Kachava (L. Yankovska, A. Tsidylo), Gnizdechna (I. Kuzyk, I Branovskyi.), Gnizna (V. Tsaryk, P. Tsaryk), Nichlavka and Nichlava (Yu. Melnyk, I. Kuzyk, L. Tsaryk). Graduate students of the Faculty of Geography conduct complex hydroecological studies of the basins of small rivers of Western Podillia, as evidenced by the published collective monograph and a number of articles in specialized scientific journals. The article highlights the geoecological problems of small rivers, such as the reclamation of wetlands, which in the conditions of aridization of the climate leads to over-draining of reclaimed lands, disruption of the water balance within river basins, which have turned into ecologically unstable lands. Daily and seasonal changes in the heat balance are observed, which affects the daily and seasonal rhythms of the bioproductivity of soil microorganisms, and therefore the processes of soil formation, renewability and stability of soils. Changes in the heat balance in conditions of aridization of the climate do not contribute to the establishment of optimal ratios between heat and moisture. The problem of disturbance of mineral metabolism in soils as a result of agricultural cultivation, when mineral fertilizers, toxic chemicals are applied to them, and mineral substances are removed from the fields along with the harvest. Annually, with the harvest of one ton of grain, up to 65 kg of the main active substances are removed from the soil. The introduction of an excessive amount of mineral fertilizers leads to their accumulation in soil horizons, and therefore in plant organisms. The problem of changing the biogenic cycle of substances is related to the processes of soil and humus formation. Extraction of a significant part of organic substances with plant products from the geosystem in the process of agricultural production, lack of adequate introduction of organic fertilizers instead leads to dehumification of soils, reduction of the capacity of their humus layer, reduction of fertility, ultimately to their depletion and degradation. In river basins, the average application of organic fertilizers has decreased tenfold - from 14 t/ha in 1990 to 0.34 t/ha in 2020, and they are not applied at all on large areas of land. Residual soil contamination with radionuclides of cesium-137 and strontium-90 remains within the limits of Polivetska, Palashivska and Bazarska village councils, located in the middle part of the Djuryn river basin. Within the basin of the Nichlava River, radiation pollution is limited to the outskirts of the settlements of Shmankivchiki, Kolindani, Davidkivtsi, Mikhalkiv, Pylypche, Ustya. Radionuclides migrated deep into the soil profiles in the watershed areas and accumulated at a depth of 80-100 cm. The conducted studies proved that the development of degradation processes in the conditions of long-term anthropogenic loads is the cause of the loss of the basin system's stability. Optimization measures based on the principle of maintaining balance and parity development of the economy and nature protection are substantiated. This means that the use of land and other natural resources and the development of economic activity in the studied territory should not deteriorate the quality of the environment and the state of natural geosystems and their geocomponents. Optimization measures provide for the improvement of the quality of the environment and the formation of an ecologically safe system of nature management Key words: historical stages, geoecological problems, small rivers, Western Podillia.