Caspian Sea water level fluctuation: comparison between ground measurements and altimetry
Mikhael Bolgov(1) , Jean-François Cretaux(2) , Muriel Bergé-Nguyen(2) , Alexei Kouraev(3) , M Filimonova(4) , and M Trubetskova(4)
Caspian Sea Laboratory,
Gubkina Street, 3,
(2) CNES/LEGOS, 14 Av Edouard Belin, 31400 Toulouse, France
(3) LEGOS, 1' Av Edouard Belin, 31400 Toulouse, France
(4) Institute of Water Problem, Gybkina Str, 3, 117971 Moscow, Russian Federation
The Caspian Sea is the largest inland water body of the world. The total basin catchment covers more than 3 billions of km2, and the sea is fed by numerous rivers including the Volga, Ural, Terek, and Kura rivers. In the last 25 years the total surface area has varied from 360000 to 400000 km2 due to high water level variations. These have shown oscillations between -26 and -29 meters (with respect to the zero ocean level) during the last hundreds years.
The Caspian Sea is characterised by quasi - cyclic and high amplitude water level variations over historical time scales. For 2000 years the fluctuation were around 15 meters and for the last five centuries ~7 meters, noting extreme level oscillations of -23 m in the mid XVII century, and -29 in 1979.
These are considerable sea level changes that merit an investigation of their causes and potential impacts. Coastal and delta areas are strongly affected by these events with subsequent damages on infrastructure and recurrent ecological disasters. Adaptation of human activities in the catchment area, efficient uses of water resources, sustainable development of the region, and ecosystem protection near and around the Caspian sea (human life, terrestrial and marine fauna and flora) fundamentally depend on the variations of the Caspian sea water level variations studies and analysis of the detailed water balance among other axes of research. The water balance of Caspian Sea is principally controlled by variations of Volga river and evaporation rate. The Volga river provide more than 80% of the total inflow, and dictates interannual variability of the Caspian sea. Other hydrological components (precipitation, evaporation, underground water, and river discharge to Kara Bogaz Goal) also influence seasonal and inter-annual variation of Caspian Sea.
Investigations of water balance is based on more than a hundred years of in-situ data based on the network of hydrometeorological stations homogeneously scattered along the coast and Islands of the Caspian Sea. Since the beginning of the nineties, however, altimetry measurements also provide precise measurements of Caspian Sea level variation. Comparison between ground measurements, hydrological in-situ data and altimetry allow to better understand the water balance of this water body. Spaitial variability of the Caspian sea level variation is also studied through altimetry measurements. This showed the major impact of Volga river discharge.