Intra-annual surface runoff distribution of The Chatkal River in different watery years

In planning water reservoirs, it’s significant to understand surface runoff behaviors, especially in medium and small rivers. The article examines water availability results during different watery years of The Chatkal River, which is the biggest left tributary of The Chirchik River. The computation of intra-annual runoff distribution for three different years of watery and for two distinguished periods of watery was carried out. It is derived that independently from the watery of year, 80% of runoff originates in high water period and 20% in the low water period.

Land Drainage Development Processes and Changes in the Context of Runoff Change in Northern Lithuania

The impact of the drainage of excessively wet land on river runoff has so far been assessed differently and very carefully because of its complexity and diversity. The article analyses changes of drained land areas and runoff in the river basins of Mūša, Lėvuo Tatula and Nemunėlis. Wet land areas in the Mūša, Lėvuo and Nemunėlis rivers basins account for more than 70% from the total basins area and in the Tatula about 90%. Increase of drained land areas in the studied river basins has no significant influence on the change of river runoff. Studies have shown that the change in drained land areas did not affect the change in runoff height. Drainage does not have a significant effect on changes in the annual runoff distribution of the studied rivers.

Estimation of the annual runoff distribution of the Siverskyi Donets River Basin in the period of current climate change

<p>The most urgent tasks facing hydrologists of Ukraine and the world include identifying patterns of rivers hydrological regime against the background of global warming, and assessing these changes. Changes in the annual runoff distribution under climate change impact require separate investigation of anthropogenically altered catchments, such as the Siverskyi Donets River Basin. Siverskyi Donets is the largest river in Eastern Ukraine and the main source of water supply for Kharkiv, Luhansk and Donetsk regions.</p><p>The annual runoff distribution of the Siverskyi Donets River Basin was evaluated by two periods: to the beginning of pronounced climatic changes and the current period. The research is proposed for three water year types: wet year, average year and dry year. The Siverskyi Donets Basin is a complicated water body with peculiar physico-geographical conditions, because of that annual runoff distribution is somewhat different for the left-bank tributaries, right-bank tributaries and, in fact, the Siverskyi Donets River itself.</p><p>It is found that the most runoff of the wet year for both periods is in the spring months. The current period is characterized by a much smaller runoff of spring flood (from the volume of annual runoff) than in the previous period. The annual runoff distribution is offset. Some differences can be observed between the left and right tributaries. For the left-bank tributaries, which has less anthropogenic load, climate change has led to a significant increase of winter and summer-autumn low flow periods. On the right tributaries of the Siverskyi Donets, which are flowing within the industrial part of the Donbass, the low flow period has not changed, or even decreased. Such situation is due to the decrease of mine water disposal because of the industrial production decrease in the region.</p><p>The largest part of the annual runoff in the average year falls on February and March. In the current period, the spring flood has decreased, but the summer and autumn low flow period has increased. The left-bank tributaries runoff during the winter low period is decrease. Instead, the runoff attributable to the autumn and winter low period has increased for the right-bank tributaries and the Siverskyi Donets itself.</p><p>Analyzing the runoff distribution of dry year, we can conclude that the most wet is February. At present, in dry years, spring flood practically are not allocated from the hydrograph; the baseflow months runoff significantly increased. The volume of winter runoff of the Siverskyi Donets River Basin is increased. Actually, for the Siverskyi Donets River the runoff of the summer period has increased and the runoff of the winter and autumn periods has decreased at the present stage.</p><p>The annual runoff distribution of the Siverskyi Donets River Basin in the current climate change has undergone significant changes: the spring flood has decreased and the summer-autumn low flow has increased.</p>

MODERN TRANSFORMATION OF SEASONAL RUNOFF DISTRIBUTION OF THE SIVERSKYI DONETS RIVER BASIN

The annual runoff distribution of the Siverskyi Donets River Basin in the period of modern climate change was estimated. The annual runoff distribution of the Siverskyi Donets Basin was researched for two characteristic periods (from the beginning of observations to 1988 and from 1989 to 2018). The assessment was performed for three water year types: wet year, average year and dry year. The research was performed for three groups of rivers depending on their affiliation to a particular part of the Basin. During the research, the average monthly runoff of the hydrological gauges, which we selected for the study were averaged. The annual runoff distribution was leveled in the current period. The Siverskyi Donets Basin is characterized by the peculiar physico-geographical conditions, so the annual runoff distribution is somewhat different for different part of the Basin. Differences in the annual runoff distribution of the right-bank tributaries, the left-bank tributaries and the Siverskyi Donets River were revealed. For the left-bank tributaries, which are less affected by anthropogenic load, climate change has led to a significant increase in runoff of the winter and summer-autumn low period. For the right-bank tributaries of the Siverskyi Donets, flowing within the industrial part of Donbas, the share of low period runoff has not changed, or even decreased. This is due to the reduction of mine drainage, due to the reduction of industrial production in the region. Instead, the share of autumn-winter period in the annual runoff has increased for the right-bank tributaries and the Siverskyi Donets River itself. It is established that the share of spring floods from the annual volume of runoff has significantly decreased and the share of the summer-autumn period for the rivers of the Siverskyi Donets Basin in the modern period has increased. The winter runoff of the left-bank tributaries of the modern period is characterized by an increase. The right-bank tributaries of the Basin are characterized by a decrease in winter runoff. Currently, in dry years, spring flood is practically not allocated on the annual hydrograph; the share of runoff in the limited months has significantly increased. At the present stage of climate change, the annual runoff distribution of the Siverskyi Donets River Basin has undergone significant changes.

Intra-annual Runoff Distribution in the Pripyat River Basin

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.

GEOLOGICAL AND HYDROGEOLOGICAL STRUCTURE OF RIVER BASINS AND SOIL COMPOSITION AS AN IMPORTANT FACTOR IN THE FORMATION OF THE STREAMFLOW OF THE TERRITORY (ON THE EXAMPLE OF THE DEBED RIVER BASIN)

The regularities of the spatial distribution of the river runoff of the Debed basin, the features of the water regime and the intra-annual runoff distribution caused by the geological and hydrogeological structure of the region and composition of soil were discussed and analyzed. Discussed some issues of regulation and management of river runoff associated with the feature of the geological and hydrogeological structure of the river basin and the composition of soil.