Изменение стока снегового половодья на южном макросклоне Русской равнины в период 1930–2014 гг

In recent decades, in the southern macro-slope (catchment) of Te Russian Plain, mainly within the basins of the Volga and the Don rivers, the spring flood flow decreased due to both anthropogenic and climatic factors. Of anthropogenic factors, the creation of reservoirs played a signifcant role in changing the water regime of the Volga and the Don. Another important factor, affecting the river runoff, is agricultural activities on flat interfluves and slopes. Compared with the conventional-natural period (for the Volga from 1879, and for the Don from 1876 to 1929) to the date (for the period 1930–2014), the flood flow of the Volga has been decreased by more than 4300 km3, and the Don – by almost 900 km3. Te contribution of anthropogenic factors to this decrease in the Volga basin exceeded 70%, and for the Don it was equal to 45%, while the climatic ones contributed 30 and 55%, respectively. During the period of instrumental observations on the rivers of the region, long-lasting phases of high/low water content with duration from 15–20 to 90 years or longer, caused by the climatic changes, were determined. Tese are a characteristic feature of long-term changes in flood flow (and in a runoff of other seasons) on both medium and large rivers of the southern macro-slope of the Russian Plain. Te period since early 2000s was a start of the decreased flood flow everywhere, i.e. on medium and large rivers. It is most clearly (by tens of percent) manifested in the decrease of the spring surface flow due to the following factors: more frequent thaws, reduction of the depth of soil freezing, increase of infltration, especially in the forest-steppe and steppe zones. Increase in flow of the infltration origin does only partially compensate the decrease of the flow in rivers.Рассматриваются сток снегового половодья в пределах бассейнов Волги и Дона и его изменения под влиянием антропогенных и климатических факторов. Изложены методы исследования изменений речного стока, оценены его изменения за последние десятилетия. Общая тенденция – уменьшение стока половодья, что связано с гидротехническим воздействием и климатическими факторами

The ensemble scenarios projecting runoff changes in large Russian river basins in the 21st century

An approach is presented for carrying out a long-term projection of river runoff changes in large Russian river basins in the first three decades of the 21st century. These changes may be caused by climate warming and socio-economic factors. The approach utilizes a method for scenario estimation of runoff changes with a range of possible climate warming effects. This range is chosen by generalizing calculation results obtained by using an ensemble of global climate models for two contrasting scenarios (A2 and B1) of globally-averaged air temperature rises. The approach also utilizes a method for alternative scenario estimation for water consumption as related to socio-economic changes. The estimates show that the expected runoff changes in the first third of this century due to climate warming scenarios can compensate the runoff decrease caused by the realization of some of the scenarios for socio-economic changes in the Volga River basin. The same compensation does not occur in the Don River basin, where negative effects are expected for the regional ecology

Change in snow flood flow in the southern macro-slope of the Russian Plain in the period 1930-2014

In recent decades, in the southern macro-slope (catchment) of Te Russian Plain, mainly within the basins of the Volga and the Don rivers, the spring flood flow decreased due to both anthropogenic and climatic factors. Of anthropogenic factors, the creation of reservoirs played a signifcant role in changing the water regime of the Volga and the Don. Another important factor, affecting the river runoff, is agricultural activities on flat interfluves and slopes. Compared with the conventional-natural period (for the Volga from 1879, and for the Don from 1876 to 1929) to the date (for the period 1930–2014), the flood flow of the Volga has been decreased by more than 4300 km3, and the Don – by almost 900 km3. Te contribution of anthropogenic factors to this decrease in the Volga basin exceeded 70%, and for the Don it was equal to 45%, while the climatic ones contributed 30 and 55%, respectively. During the period of instrumental observations on the rivers of the region, long-lasting phases of high/low water content with duration from 15–20 to 90 years or longer, caused by the climatic changes, were determined. Tese are a characteristic feature of long-term changes in flood flow (and in a runoff of other seasons) on both medium and large rivers of the southern macro-slope of the Russian Plain. Te period since early 2000s was a start of the decreased flood flow everywhere, i.e. on medium and large rivers. It is most clearly (by tens of percent) manifested in the decrease of the spring surface flow due to the following factors: more frequent thaws, reduction of the depth of soil freezing, increase of infltration, especially in the forest-steppe and steppe zones. Increase in flow of the infltration origin does only partially compensate the decrease of the flow in rivers