Studying the Spatiotemporal Variability of the Components of the North Caspian Sea Water Balance Using the Water Balance Model

L. P. Ostroumova and V. F. Polonskii

Considered is the water balance model of the estuarine seaside of the Volga and Ural rivers and the North Caspian Sea as well as of its separate parts. The following computational spatial elements, three parts of the North Caspian Sea, are singled out: the shallow zone of the Volga River estuarine seaside, the deep zone in the western part of the North Caspian Sea, and the eastern part of the North Caspian Sea. The input parameters in this model are evaporation from the water surface computed using the ISPAR technique and precipitation depth corrected using the technique of the correction of the measured amount of precipitation worked out by the Main Geophysical Observatory and Kazakh Research Hydrometeorological Institute. The computations are based on the data of observations at four weather stations: Zelenga (Russia), Peshnoi Island, Kulaly Island, and Fort Shevchenko (Kazakhstan). The water inflow to the Volga River delta top corrected by the value of natural evaporation loss in the delta is used as the water inflow to the North Caspian Sea. The water inflow from the Ural River delta to the North Caspian Sea is estimated from the data of Makhambet hydrological station. Using the water balance model, the water balance components can be computed for the separate parts of the North Caspian Sea and the water balance equation can be solved regarding the water balance outflow from these parts. The volume of the water outflow from the North Caspian Sea to the Middle Caspian Sea is determined as a result of water exchange between them. The variations of basic components of the North Caspian Sea following different typical scenarios (typical years determined from the Volga River runoff) are computed using its water balance model. Analyzed are the spatiotemporal regularities of water redistribution in the North Caspian Sea with account of the river runoff volume, evaporation loss, and amount of precipitation at different background levels of the Caspian Sea.