The Caspian Sea has recently been increasingly exposed to the anthropogenic impacts associated with the active economic development of its waters. Under these conditions, knowledge of the hydrological regime of the sea and its changes, which largely determine the ecological situation, is of practical importance. However, the Caspian Sea hydrological regime, especially its variability, is poorly studied. Given the lack of observational data, the role of mathematical modeling of the sea regime increases significantly, since it allows numerical experiments to diagnose and predict the hydrological state of waters without significant material costs considering the anthropogenic impact. Such an approach, when the study of level fluctuations according to field data is combined with hydrodynamic modeling and numerical experiments, expands the possibilities of scientific analysis.
In relation to the problem of studying fluctuations in the level of the Caspian Sea, the following tasks are mainly solved by numerical hydrodynamic modeling:
To reveal the role of the various factors that cause the water level fluctuations in specific physic-geographical conditions.
• To develop the methods of calculation of the sea level and its extreme characteristics for practical l employment into hydraulic engineering, industrial and municipal designing, and construction.
• The study of the water level fluctuations regime for areas, is not enough or completely not shined by observed data.
• To execute a probability estimation of the future water level regime for the needs of various large economic actions (construction of dams, protective dams, withdrawals of a rivers runoff, etc.).
• To develop the forecast methods of the water level fluctuations.
To solve these problems, the MIKE 21 hydrodynamic module developed at the Danish Hydraulic Institute (DGI) is used, which is the main module of the entire MIKE 21 simulation system and provides a hydrodynamic basis for calculations. It simulates changes in the water level and flows in response to the phenomena occurring in the reservoir. Water levels and flows are decomposed in a rectangular coordinate grid covering the space of interest, subject to the availability of bathymetric data, bottom roughness coefficients, wind fields, hydrographic boundary conditions, etc. The hydrodynamic module of the model solves the system of vertically integrated equations of continuity and conservation of momentum in two horizontal dimensions, achieving good spatial and temporal resolution, and investigates the effect of disturbances rapidly changing under the influence of atmospheric processes on this layer on the dynamics of the underlying layer.
Storm Surges Forecast for the Various Zones of the Caspian Sea Kazakhstan’s Coast
Storm surges in the sea are short-term non-periodic changes in the sea level under the influence of wind and atmospheric pressure. As a result of this effect, the translational movement of water occurs in the surface layer of the sea, causing movement of water masses, which leads to short-term fluctuations in sea level near the coast. Extensive shallow lands, the small slope of a bottom and land, a configuration of coastal feature, the vigorous activity of wind create favorable conditions for development in the Northern Caspian Sea the significant storm surges. There are essential changes in hydrology-morphological, hydrochemical, and ecological processes because of the storm surges at the coastal zone of Near-Caspian lowland.
During the modern period when the Caspian Sea high background level the storm surges are accompanied by flooding of greater areas, that were flood-free sites at one time on Kazakhstan’s coast. It brings huge losses to economic objects, the population, and the ecology of the region. In the Northern Caspian Sea, the water level falling can reach 2,5 m during negative storm surges. It will cause an infringement of work of water-fences, the drying up of port water areas and navigable sea channels, reduction of the spawning and the areas valuable food fishes fattening, first of all - sturgeon, change of landscape structure of coastal territories, and desertification of coastal areas. In the open part of the sea more remote from the coast at significant negative storm surges conditions for pass of courts worsen, and they go with underloading. Negative storm surges limit pass on Mangishlak’s a threshold. The caused damage can be considerably lowered by the preliminary prevention storm surges.
The sea-level forecast is made as a table two times a week (Tuesday and Friday) for two economic regions of Kazakhstan (Atyrau and Mangistau region), adjoining to the Caspian Sea. The numerical weather forecasts from the European Middle Weather Forecast Center (UK) are the basis of the sea-level forecast. The sea-level forecasts are made for eight stations chosen with the account morphometry conditions and specificity of the synoptic processes of this region. Such basic stations are Zhambay, Peshnoy Island, Karaton, Kalamkas, Kulaly Island, the Fort-Shevchenko, Aktau, and Fetisovo. Except for that sea-level forecasts are made for two Russian stations: Tyuleniy Island and Makhachkala for which daily on an interstate exchange the operative hydrometeorological information turns out, enabling to estimate the accuracy of let out forecasts. Step-type behavior of a sea-level calculation (forecast) is one hour, earliness - till 120 hours (5 days). The maximal, minimal, and average levels for the period of the forecast also are presented in the table. The storm surges forecasts are specified every day at threat of occurrence dangerous. The estimation of accuracy of the forecast is carried out by comparison of the measured and observed sea level based on the tables.
Developed in RSE «Kazhydromet» the system of the water level forecasting allows put out the forecast information for ANY point set by the consumer.
Weekly Caspian Sea Bulletin
The sea-level forecast is made based on the received results of hydrodynamical modeling. The bulletin is made in electronic and printed versions.
The Summer Weekly Caspian Sea Bulletin includes the review of the sea-level state for the previous week and the sea-level forecast for 5 days forward in a graphic kind. In our bulletin are submitted a table with criteria of the danger of the storm surges for the Caspian Sea northeast coast and a table with maximal, minimal, and average values of the forecasted sea level for stations for the period of earliness.
During wintertime, there is the Winter Weekly Caspian Sea Bulletin. In this variant the condition of a Caspian Sea water table is displayed, the level forecast of a nonfreezing part of the sea is given. In the Winter Bulletin the review of ice conditions at the Kazakhstan stations is given and graphic of water temperature for marine stations, space pictures are submitted also.
Great importance for the regions of the Middle Caspian have wave forecasts. To solve this problem, a wave forecast methodology based on the Bretschneider curve was developed. To improve the forecasting of waves, the wave spectral model SWAN was adapted to the conditions of the Caspian Sea and introduced into production.
Using these technologies, a bulletin and wave forecasts are issued with a lead time of 5 days for 3 squares of the open water area of the Caspian Sea, as well as Bautino and Kuryk bays. In accordance with the agreements, a methodology has been developed and wave forecasts for oil production areas are issued. Information obtained from the European Center for Medium-Range Weather Forecasts is also used as an input characteristic.
Caspian Sea Ice Monitoring
Caspian Sea ice reviews are issued weekly during the winter period. After the ice period finishing summary tables of the Caspian Sea ice basic characteristics made based on materials of urgent supervision on each sea hydrometeorological station. Then the tables are published in the «Annual data about of a Caspian Sea waters regime. Kazakhstan’s coast».