GROUPINGS OF YEARS OF DIFFERENT MOISTURE, WATER CONTENT AND EVAPORATION OF LOCAL CATCHMENTS OF THE LOWER VOLGA RESERVOIRS
V.I. Babkin, A.V. Babkin, E.L. Skoryatina
State Hydrological Institute, Saint Petersburg, Russia
Keywords: precipitation, runoff, change of water content within a local catchment, correlation of water balance elements, three ranges of values of water balance elements, probability of transition from one range of values to another
Abstract
A methodology is proposed and an assessment of water balance elements of the local catchments of the Kuibyshev, Saratov and Volgograd Reservoirs is carried out based on the data of the regional offices of Roshydromet. The studies were developed for the period of 1966-2017. The methodology is based on taking into account the data on atmospheric precipitation, evaporation and runoff from the local catchments of the Lower Volga reservoirs. Evaporation from the catchment areas was estimated using the method of A.R. Konstantinov taking into consideration the respective series of air temperature and pressure of water vapor. The balance element, taking into account the accumulation (loss) of water content within the local catchments, was determined by the difference between atmospheric precipitation and the sum of runoff and evaporation. When moving upriver from the Volgograd Reservoir to the Kuibyshev one, evaporation from the catchments under consideration, as well as the correlation of its time series with atmospheric precipitation, consistently decrease. Accordingly, precipitation, local runoff and their correlation increase. Simultaneously, for the studied reservoir catchments the groupings of years of high, low and close to average values for the period 1966-2017 were estimated for precipitation, evaporation and runoff. It was concluded that the presence of these groupings during this period is strictly individual. The lengths and different sequences of alternation of groupings of years of the water balance elements can be signs of certain patterns in their fluctuations. The article estimates probabilities of transition of water balance components from one range of values to another. In some cases, probability of transition of a water balance element from one range of values to another, or its preservation in the current range, is quite high and amounts to 50 % or more, or may be small - close to 0. Such information can be useful in predicting the transition with the appropriate lead time.
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