Transformation of the river network of the left-bank tributaries of the Middle Dnipro

The dissertation work involves researching the transformation of the river network within the left tributaries of the Middle Dnipro. Methodological foundations of the research have been defined, and a retrospective analysis of river network studies has been conducted. The data on the characteristics of the conditions for forming the river runoff in the studied part of the sub-basin have been analyzed, including geographical, geological, hydrogeological, climatic, and soil-vegetation conditions, as well as the impact of economic activities and landscape-hydrological zoning. An analysis of the hydrological regime of the left tributaries of the Middle Dnipro within two key hydroclimatic periods, 1961-1990 and 1991-2020, has been carried out; calculations of the water balance and intra- annual distribution of river runoff in the studied basin have been performed. Information on the transformation of the hydrographic network of the left tributaries of the Middle Dnipro during the anthropogenic period has been summarized. The change in the river network during the 19th-20th centuries and the modern period has been studied, and a forecast for further transformation within the 21st century has been provided. Based on the obtained data, a dynamic cartographic model of the transformation of the river network of the left bank of the Middle Dnipro has been created.
The main results of the research can be used by the Poltava Regional Hydrometeorological Center to analyze multi-year changes in hydrometeorological conditions in the area of responsibility; to characterize the hydrographic network and populate the Catalog of rivers, channels, lakes, and reservoirs of the State Water Cadastre; to provide consumers with hydrological information on the main trends in changing characteristics of river water regimes. The main results of the research can also be used in making management decisions regarding the optimization of the hydrological observation network.
The aim of the dissertation is to conduct a comprehensive analysis and study of the transformation of the river network within the basins of the left tributaries of the Middle Dnipro.
The object of the study is the river network of the basins of the left tributaries of the sub-basin of the Middle Dnipro - 5 medium-sized ones: Psel, Vorskla, Sula, Trubizh, Supii, and a series of small river basins in the studied region - Zolotonoshka, Irklii, Kovrai, Kovalivka, Kryva Ruda, Kahamlyk, Kobeliachok, Darnytsia, Pryrva, Ikva-Pavlivka, Ruda-Horikhivka, and others.
The subject of the research is the process of transformation of the river network within the basins of the left bank tributaries of the Middle Dnipro as a result of climatic changes and anthropogenic activity. The period of regular hydrospace observations for the 20th and 21st centuries is taken into account, as well as the calculation of the transformation of the length, quantity, and density of the river network based on cartographic data from the 19th to the 20th centuries.
The work analyzes the transformation of the river network within the left tributaries of the Middle Dnipro. Methodological foundations of the research have been defined, and a retrospective analysis of river network studies has been conducted. The data on the characteristics of the conditions for forming the river runoff in the studied part of the sub-basin have been analyzed, including geographical, geological, hydrogeological, climatic, and soil-vegetation conditions, as well as the impact of economic activities and landscape-hydrological zoning. An analysis of the hydrological regime of the left tributaries of the Middle Dnipro within two key hydroclimatic periods, 1961-1990 and 1991-2020, has been carried out; calculations of the water balance and intra-annual distribution of river runoff in the studied basin have been performed. Information on the transformation of the hydrographic network of the left tributaries of the Middle Dnipro during the anthropogenic period has been summarized. The change in the river network during the 19th-20th centuries and the modern period has been studied, and a forecast for further transformation within the 21st century has been provided. Based on the obtained data, a dynamic cartographic model of the transformation of the river network of the left bank of the Middle Dnipro has been created.
During the writing of the dissertation research, data from multi-year observations from 22 hydrological posts in the basins of the left tributaries of the Middle Dnipro - Psel, Sula, Vorskla, Trubizh, Supii, and Zolotonoshka from the time of the first observations to 2020 inclusive have been used. Data from the published multi-year hydro-meteorological observation data of the State Water Cadastre of the Central Geophysical Observatory named after Boris Sreznevsky (Kyiv) were processed and summarized. Data from the reporting of the Poltava Regional Hydrometeorological Center were used.
To study the climatic features of the studied part of the Middle Dnipro basin, climatic data from the Climatic Research Unit gridded Time Series, climate data in squares of 0.5° latitude by 0.5° longitude of the Earth's geographic grid, obtained by interpolating monthly climatic anomalies from branched observation networks of weather stations, have been used. Climatic data for the studied region of the left bank of the Middle Dnipro were used from 1900 to 2020.
Original digital data from the United States Geological Survey (Shuttle Radar Topography Mission (SRTM), digital elevation model), Global Forest Watch (data and tools for forest monitoring), HydroSHEDS (global maps of watershed boundaries, river lines, and lake shorelines), IPCC WGI Interactive Atlas, Climate Knowledge Portal (WMO data on climate change under the SSP2- 4.5 scenario), KNMI Climate Change Atlas (WMO climatic and hydrological data series from 1861 to 2100) have been processed.
Geographical maps also served as source data: military-topographic map of the Russian Empire from 1846-1863 by T.F. Schubert with a scale of 3 versts in 1 inch (1.26 km in 1 cm), topographic map of the General Staff of the USSR from 1954-1977, updated from 1980-1990, with scales of 1:100000 and 1:200000. Additional sources of information included maps from the General Staff of the Red Army from 1936-1942 executed at a scale of 1 cm - 500 m and maps of the German army from 1938-1943, also executed at a scale of 1 cm - 500 m. Satellite image data from open information databases such as Google Earth Pro, EOSDA LandViewer, and NASA Worldview were utilized for the studied area.
A theoretical-methodological approach to the fundamentals of studying the transformation of the river network as an object of hydrological-geographical analysis has been substantiated and formed. The hydrological-geographical analysis method was utilized for this purpose. Relevant literature on the subject was processed, and previous studies were considered. Methodological foundations for studying the transformation of the river network were identified. They included the use of cartographic analysis methods, the technique of vectorization of the investigated hydro network, analysis of stream orders, and determination of the transformation coefficient. The history of studying the left bank of the Middle Dnipro from the 4th century BC to the modern period was investigated through the method of retrospective analysis. The main periods of hydrological-geographical research and their temporal boundaries were justified, and the main stages of hydrological-geographical research were identified within each period.
Through the hydrological-geographical analysis method, causal relationships between geographical features of the territory and the nature of surface waters of the studied river basins were established. The basin method of research allowed for a comprehensive analysis of the physical-geographical characteristics of the river basins of the left bank of the Middle Dnipro, including their geographical location, tectonic, geological, hydrogeological structure, climatic features, and soil- vegetation cover of the investigated river basins. Detailed information on the economic use of the river basins of the left bank of the Middle Dnipro in agriculture, industry, recreation, fishing, navigation, and other areas was summarized. Key natural and anthropogenic influences on the river network of the studied sub-basin were identified.
The data on the characteristics of climatic-hydrological conditions, runoff formation conditions, and hydrological regime of the left tributaries sub-basin of the Middle Dnipro have been summarized and updated for two climatic periods: 1961-1990 and 1991-2020. In the modern climatic period of 1991-2020, a decrease in annual precipitation compared to the previous period of climatic norms was observed, along with an increase in the average annual air temperature by +1.3°C. The relationship between landscape and the hydrological regime of rivers in the studied region was assessed using the landscape-hydrological research method.
Using mathematical and statistical research methods, hydrological parameters such as multi-year, average annual, seasonal, and average monthly runoff volumes were calculated. Additionally, the percentages of different types of runoff feeding within the 18 hydrological posts of the left bank region of the Middle Dnipro were determined. The analysis of average monthly runoff rates for two 30-year hydrological cycles, 1961-1990 and 1991-2020, confirmed a decrease in groundwater (-2%) and snowmelt (-3%) contributions. However, against the backdrop of a general decrease in river runoff, there was an increase in the proportion of rainfall-fed runoff by +5%.
Using the water balance method, an assessment and comparison of the components of the water balance for the watersheds in the Ukrainian parts of the Psel, Sula, Vorskla, Trubizh, Supii, and Zolotonoshka basins were conducted for characteristic periods of 1961-1990 and 1991-2020. It was determined that over the last 30 years (1991-2020), there has been a general increase in aridity coefficients and a decrease in runoff coefficients. Overall, the aridity coefficient within the left bank region of the Middle Dnipro increased by 0.9%, reaching 95.4%. This increase is attributed to the decrease in surface runoff of rivers by -5.2 mm/year, atmospheric precipitation by -7.3 mm/year, and total evaporation by -2.1 mm/year.
The study summarizes the research on the origin and development of the river network of the Middle Dnipro during the Anthropogenic period. Special attention is given to the influence of the Dnieper and Valdai (Saalian and Weichselian) glaciations on the river network of the region. The geography of fluvio-glacial streams, water bodies, and watercourses within the left bank of the Middle Dnipro is determined.
A retrospective analysis of the transformation of the river system of the left tributaries of the Middle Dnipro during the 19th - 21st centuries was conducted based on the cartographic method using overlaying of maps from different time periods and satellite imagery (1985-2020). This analysis allowed for calculating the total length of the river network, the number of watercourses, and the density of the river network both across the entire left bank of the Middle Dnipro and within each of the key river basins.
The transformation of the hydrographic network within two small river basins - Kovzhyzha and Chorna, during the 19th - 21st centuries, was investigated using field and cartographic methods.
Using GIS methods, remote sensing of the Earth, and the cartographic method, a dynamic cartographic model of the left bank basin of the Middle Dnipro from the 19th to the 21st centuries was created. This model demonstrates the transformational changes of the river network during the respective periods based on the obtained and projected results.
A forecast of further transformation of the hydrographic network of the left tributaries of the Middle Dnipro until 2100 was provided based on the SSP2 climate scenario. The total length of all rivers within the study basin is expected to decrease by 4479 km by the end of the 21st century. This reduction will particularly impact the basins of the largest river systems, such as the Psel, Vorskla, and Sula. Small rivers such as Kryva Ruda and Kovalivka may experience catastrophic consequences, such as drying up or loss of their river network.

Сарнавський С. П. Трансформація річкової мережі лівобережних приток Середнього Дніпра : дис. … д-ра філософії : 103 Науки про Землю / Сарнавський Сергій Петрович. – Київ, 2024. – 278 с.