The paper presents long-term changes in water temperature in two rivers, Oder and Neman, with catchments showing different climatic conditions (with dominance of marine climate in the case of the Oder and continental climate in the case of the Neman River). A statistically significant increase in mean annual water temperature was recorded for four observation stations, ranging from 0.17 to 0.39 °C dec⁻¹. At the seasonal scale, for the winter half-year, water temperature increase varied from 0.17 to 0.26 °C dec⁻¹, and for the summer half-year from 0.17 to 0.50 °C dec⁻¹. In three cases (Odra-Brzeg, Odra-Słubice, Niemen-Grodno), the recorded changes referred to the scale of changes in air temperature. For the fourth station on Neman (Smalininkai), an increase in water temperature in the river was considerably slower than air temperature increase. It should be associated with the substantial role of local conditions (non-climatic) affecting the thermal regime in that profile. Short-term forecast of changes in water temperature showed its further successive increase, a situation unfavorable for the functioning of these ecosystems.

The research results of runoff changes in the River Viliya at 3 stations (Steshitsy Village, Vileyka Town and Mihalishki village) during the period 1946–2014 for the average annual, maximum, minimum summer-autumn and winter runoff are presented. It has been concluded that heterogeneity in the time series of the river runoff is caused by natural-climatic and anthropogenic factors. At Mihalishki Village the average annual runoff is about 59.7 m³ s–1, the maximum 1570 m³ s–1, minimum summer–autumn is 22.0 m³ s–1, the minimum winter runoff is 17.3 m³ s–1, and the environmental runoff is 21.1 m³ s–1. A forecast of runoff changes for the River Viliya, depending on forecasted climate change using the “Atlas of Global and Regional Climate Projections” was made on the basis of four scenarios RCP8.5, RCP6.0, RCP4.5, RCP2.6. The results of research indicate that significant changes in runoff will not occur as the forecasted climatic parameters did not change significantly. A forecasted decrease in spring runoff was investigated, thus reducing the minimum runoff is not essential. In the event of possible low water periods the Vileyka reservoir resources, involving the Olkhovskoye and the Snigyanskoye water reservoirs, can be used for compensation measures, which may be considered as the most reliable backup source of industrial water supply for the Belarusian Nuclear Power Plant.

The article is devoted to the problems of water resources in Belarusian Polesie. Surface water resources analysis was carried out for the different types of runoffs. There was a significant decrease in maximum spring runoff and a decrease in the average annual runoff. A statistically significant increase in the minimum winter runoff is observed for the rivers of the Pripyat River basin. For the minimum summer–autumn runoff, there was no unambiguous trend in the runoff change. Quality of natural waters analysis included investigation of the annual concentrations of priority substances in the water of some rivers in Polesie for dissolved oxygen, phosphates, nitrogen, petroleum products, copper, zinc, etc. In general, there have been trends toward a pollution decrease in the Polesie Rivers. The possible consequences of changes in river runoff due to climate change are considered. The priority tasks of research on solving the Polesie water problems are outlined.

The time variability features of the intra-annual runoff distribution in the Pripyat River basin at the present stage are considered. The study used data from 10 active gauging-stations at the basin area for the period of enabled observations. Changes in the nature of natural runoff regulation of rivers are shown. An increase in the coefficient of natural runoff regulation after the period 1970-1983 for the rivers of the Pripyat River basin was revealed. The relationship between the coefficient of uneven runoff and the share of spring flood was established.

В статье выполнена оценка изменений характеристик годового стока, максимального стока весеннего половодья и основных стокоформирующих факторов за период 1988−2018 гг. по отношению к периоду 1949−1987 гг. Установлено, что отмечаемые за последние десятилетия климатические изменения существенно меняют картину пространственно-временной изменчивости максимального стока. Изменения же годового стока для большинства водосборов Беларуси носят статистически незначимый характер. Основными климатическими факторами, определяющими сток весеннего половодья, являются осадки за зимний и весенний периоды, температура воздуха зимнего периода. С учетом мультимодельного ансамбля из четырех сценариев изменения климата получены прогнозные оценки годового и максимального стока на период до 2035 г.

The work is devoted to assessing changes in the water regime of the Lan River in modern conditions and the near future with the aim of developing a strategy for the rational use of the water potential of small rivers in the Belarusian Polesie region. There was a tendency towards an increase in annual runoff at the Loktyshi and Mokrovo gauging stations during the study period from 1948 to 2015, which was caused by anthropogenic factors in the form of amelioration measures; and in the upper reaches of the river at the Lognovichi gauging station there was a slight decrease in runoff caused by climatic influences. Testing the hypothesis about the homogeneity of the runoff series under consideration for periods with different averaging intervals has showed heterogeneity for some types of runoff. This was caused by intensive economic activity, which significantly disrupts the natural hydrological regime. A runoff forecast was made for the Lan River at the Mokrovo gauging station for the period up to 2035 based on archive of meteorological data using a multi-model ensemble of four CMIP5 scenarios. A slight decrease in runoff was predicted, caused by additional evaporation from the water surface of the reservoir due to increased air temperature, as well as a slight shift in the peak of the spring flood to March. Работа посвящена оценке изменений водного режима реки Лань в современных условиях и на ближайшую перспективу с целью разработки стратегии рационального использования водного потенциала малых рек Белорусского Полесья. За исследуемый период с 1948 по 2015 г. на гидропостах Локтыши и Мокрово наблюдалась тенденция к увеличению годового стока, что было обусловлено антропогенными факторами в виде проведения мелиоративных мероприятий, а в верховьях реки на гидропосте Логновичи наблюдалось некоторое уменьшение стока, вызванное климатическими воздействиями. Проверка гипотезы об однородности рассматриваемых рядов стока для периодов с различными интервалами осреднения показала неоднородность по некоторым типам стока. Это обусловлено интенсивной хозяйственной деятельностью, которая существенно нарушает естественный гидрологический режим. На основе архива метеорологических данных с использованием многомодельного ансамбля из четырех сценариев CMIP5 выполнен прогноз стока реки Лань в створе Мокрово на период до 2035 г. Прогнозируется незначительное уменьшение стока, вызванное дополнительным испарением с водной поверхности водохранилища из-за повышения температуры воздуха, а также небольшим смещением пика весеннего половодья на март.