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Льодостав, який утворюється на річках в осіннє-зимовий період суттєво впливає на гідрологічні, гідрохімічні, біологічні процеси річок, а також роботу гідроенергетики, судноплавства, рибного господарства тощо. У сучасних умовах формування, тривалість, руйнування льодоставу на річках відбувається під впливом природних, антропогенних чинників та кліматичних змін. Дослідження сучасних тенденцій тривалості льодоставу річок та визначення його розрахункових характеристик є актуальним завданням. У даній роботі визначено ймовірнісні характеристики, статистичні параметри тривалості льодоставу на річках басейну Прип’яті у межах України. Використано дані 29 гідрологічних постів за період від початку спостережень по 2020 р. включно. В якості статистичних параметрів аналітичного розподілу тривалості льодоставу річок використано середнє багаторічне значення, коефіцієнт варіації і коефіцієнт асиметрії, які розраховувались методом моментів. Розподіл Пірсона ІІІ типу використано для побудови аналітичних кривих, а формулу Вейбула – емпіричного розподілу. Ймовірнісний розподіл Пірсона ІІІ типу цілком задовільно описує емпіричні точки тривалості льодоставу на річках басейну Прип’яті у межах України. Переважна більшість аналітичних кривих розподілу тривалості льодоставу мають від'ємну асиметрію і тільки 8 – додатну асиметрію. Середня тривалість льодоставу по басейну Прип’яті складає 69 діб і коливається у межах від 26 діб до 95 діб. Значення коефіцієнтів асиметрії невеликі і змінюються у межах від 0,01 до 1,02 для додатних значень і від -0,03 до -0,60 для від’ємних значень. Коефіцієнти варіації змінюються у невеликих межах від 0,34 до 0,79. Розраховані стандартні похибки статистичних параметрів аналітичних кривих розподілу тривалості льодоставу на річках є цілком прийнятними.

Long-term forecasting of the ice regime at the Dnipro Cascade Reservoirs is very important, first of all, for the operation of hydroelectric power stations. In addition, such forecasts also ensure the work of other sectors of the economy, namely shipping, fisheries, municipal engineering, etc. At present, the Department for hydrological forecasting of the Ukrainian Hydrometeorological Center uses techniques developedin the middle and in thesecond half of the 20th century to compile long-term forecasts and advices about the ice regimeof water bodies of Ukraine. These techniqueswere developed only for rivers;for reservoirs,they are currently lacking. The main objective of our research is to develop methods for long-term forecasting of ice break-up and disappearance at the Dnipro Cascade Reservoirs by teleconnection indicators. The research was based on the recordsfor 35 water gauges located on 6 reservoirs of the Dnipro Cascade, including the destroyed Kakhovka reservoir. The dates of the ice break-up and disappearance were used for the period from the beginning of observations at each water gauge to 2020. Moreover, the teleconnection indicators were used, namely 34 atmospheric indices, sea surface temperature indices, teleconnection indices and patterns determined by the National Weather Service (NWS) of the National Oceanic and Atmospheric Administration of United States of America (NOAA USA). Methods of the long-term forecasting of the ice break-up and disappearance at the reservoirs of the Dnipro Cascade have been developed by searching for the best correlation or regression relationship between dates and teleconnection indicators. The probable of accepted errorsof the developed methods are in the range of 62—71 %, which corresponds to satisfactory method quality that makes it possible to recommend them for use.

The current work addresses one of the key building blocks towards an improved understanding of flood processes and associated changes in flood characteristics and regimes in Europe: the development of a comprehensive, extensive European flood database. The presented work results from ongoing cross-border research collaborations initiated with data collection and joint interpretation in mind. A detailed account of the current state, characteristics and spatial and temporal coverage of the European Flood Database, is presented. At this stage, the hydrological data collection is still growing and consists at this time of annual maximum and daily mean discharge series, from over 7000 hydrometric stations of various data series lengths. Moreover, the database currently comprises data from over 50 different data sources. The time series have been obtained from different national and regional data sources in a collaborative effort of a joint European flood research agreement based on the exchange of data, models and expertise, and from existing international data collections and open source websites. These ongoing efforts are contributing to advancing the understanding of regional flood processes beyond individual country boundaries and to a more coherent flood research in Europe.

Climate change has led to concerns about increasing river floods resulting from the greater water-holding capacity of a warmer atmosphere 1 . These concerns are reinforced by evidence of increasing economic losses associated with flooding in many parts of the world, including Europe 2 . Any changes in river floods would have lasting implications for the design of flood protection measures and flood risk zoning. However, existing studies have been unable to identify a consistent continental-scale climatic-change signal in flood discharge observations in Europe 3 , because of the limited spatial coverage and number of hydrometric stations. Here we demonstrate clear regional patterns of both increases and decreases in observed river flood discharges in the past five decades in Europe, which are manifestations of a changing climate. Our results-arising from the most complete database of European flooding so far-suggest that: increasing autumn and winter rainfall has resulted in increasing floods in northwestern Europe; decreasing precipitation and increasing evaporation have led to decreasing floods in medium and large catchments in southern Europe; and decreasing snow cover and snowmelt, resulting from warmer temperatures, have led to decreasing floods in eastern Europe. Regional flood discharge trends in Europe range from an increase of about 11 per cent per decade to a decrease of 23 per cent. Notwithstanding the spatial and temporal heterogeneity of the observational record, the flood changes identified here are broadly consistent with climate model projections for the next century 4,5 , suggesting that climate-driven changes are already happening and supporting calls for the consideration of climate change in flood risk management.

A warming climate is expected to have an impact on the magnitude and timing of river floods; however, no consistent large-scale climate change signal in observed flood magnitudes has been identified so far. We analyzed the timing of river floods in Europe over the past five decades, using a pan-European database from 4262 observational hydrometric stations, and found clear patterns of change in flood timing. Warmer temperatures have led to earlier spring snowmelt floods throughout northeastern Europe; delayed winter storms associated with polar warming have led to later winter floods around the North Sea and some sectors of the Mediterranean coast; and earlier soil moisture maxima have led to earlier winter floods in western Europe. Our results highlight the existence of a clear climate signal in flood observations at the continental scale., (Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)