CASPIAN SEA COAST

Estimation of the influence of level the Caspian Sea rise
on forming of subsoil waters in the coastal zone
by simulation methods

The rise of the water level in the Caspian Sea give essential losses for economy. The industrial objects, pastures are sunk. Irrigating massives are put out of action. Objects of the oil and gas complex become source of pollution for coastal zone. It is potential threat to biological resources of the sea. The rise of the water level in the Caspian Sea cause the rise of the subsoil water level. The swamping of the territories, drowning a little of the foundations of dwelling and industrial objects, lines of electricity transmission, pipe-lines are consequences of this. In accordance with data of Scientific and Research Institute for Monitoring of Environment of the Republic Kazakhstan prognostic state of the water level in the Caspian Sea may reach the absolute elevation from 26 to 22m. The modeling of the hydrogeological conditions of the coast was executed for an estimation of influence of the current level rise of the Caspian Sea on state of surface of the subsoil waters. System with 3 levels of the interconnected models thats structure is given on figure was created.

Models system of the Kazakhstan part of the coast of the Caspian Sea

1 - regional model; 2 - model of the Ural river's lower reaches; 3 - Atyrau city model.

It consist from regional model of the Kazakhstan part of the coast of the Caspian Sea (scale 1:500 000), model of the Ural river lower reaches (scale 1:200 000) and model of the subsurface waters for Atyrau city (scale 1:10000).

Restoration of hydrogeological conditions for the year 1977 has been made by the way of solution of reverse stationary task on each model. Values of areal feeding and discharge, flows as of outer boundaries of the I-st and II-nd order, filtrational properties of water-bearing rocks have been adjusted at the process of the solution. Groundwaters levels marks agreement, measured as of boreholes and produced on the models has been as the criterium of adequacy of the models with the real hydrogeological conditions. The precision of the solution given equal: for the regional model - 2m, for the model of the 2-nd order - 1m, for the model of the 3-nd order - 0.5m. Results of the solution are given on the Figure.

Integrated maps of hydroisohypses (result of the solution of the reserve stationary task):

A - Kazakhstanic part of Caspian sea shore, B - downstreams of the Ural river, C - region of the Atyrau city
1 - initial state of hydroisohypses as of the state for the year 1977; 2 - position of hydroisohypses, received on the model; 3 - contours of assignment of boundary conditions of the first kind; 4 - Ural river, schematized by the boundary conditions of the first kind; 5- contours of assignment of boundary conditions of the second kind; 6- contours of the model- model-inset map of the first level; 7 - contours of the model-inset map of the second level; 8 - contours of the territory of Atyrau city; 9 - shore line of Caspian sea

6 variants of the predictions for sea level elevations 27, -26, -25, -24, -23, -22 m was calculated on the regional model. Prediction was executed on the term for 30 years. It was assumed that the rise on the Caspian Sea goes on instantaneously. Compiled prognostic maps of the contour of water tables was given on Fig. Also the regions of the head of subsurface waters in coastal zone was given on the maps.

Forecasted level surface of groundwaters

of Kazakhstanic part of Caspian sea shore as of the state
for the year 2028 under absolute mark of water level in sea -27 m

Prediction maps of the contour of water table of the Kazakhstan part
of the coast of the Caspian Sea on the period to 2028
(compiled V.V.Veselov, V.Yu.Panichkin)
k22_1 k22_2 k22_3 k23_1 k23_2 k23_3
k24_1 k24_2 k24_3 k25_1 k25_2 k25_3
k26_1 k26_2 k26_3 k26_1 k26_2 k26_3
Legend
1 - contour of water table in 2028, 2 - contour of the indication of the border terms of I kind, 3 - contour of the indication of the border terms of II kind, 4 - net approximation of the modeled region (numbers - numbers of the lines and columns, 5 - zone of the head of water from the side of the Caspias Sea (size of the head to 0.3 - 0.5 m, 6 - coastal line (note of he sea is indicated on Fig).

Analysis show that an extensive areas will turn out to be under water as a result of the possible further rise of the Caspian Sea level. Present time their total area in limits of the modelled region is 14.8 ths. sq. km (for sea elevation 27 m). For elevation 22 m, it will increase to 37.3 ths. sq. km.
Conclusion may be, if you compare results of the different prediction variants, as a rule, zone width for head not more 5-10 km. Its state in plan is determined firstly by prognostic level of water in the Caspian Sea (by prediction variant) and by relief of the coastal zone. Size of the prognostic rise of subsoil water level by comparison with its state present time averages mainly not more 30 50 cm, and it increase to 1 2 m, rarely to 3 4 m only in immediate near from coastal line. This size depends from absolute elevations of level surface of subsoil waters in the coastal zone for undisturbed conditions. Prognostic rises of the levels are more for areas with low elevations.
Surge phenomenons play certain role for creation of the level regime of subsoil waters in coastal part. Duration of the surge, its height, steepness of shore and area of submerged territory, thickness of the aeration zone and its filtration properties influence on volumes of the marine water coming in water-bearing horizon. Short-term (from 6 to 20 days) rises of the subsoil water levels was fixed by experimental way, its amplitude is 0.1 0.4 m. Estimation of the surge phenomenons influence on subsoil waters was executed also on the model of the Atyrau city territory [Veselov V.V. Mirlas V.M., Panichkin V.Yu. Prediction of the subsoil waters level under the effect of the head from the side of the Caspian Sea //The Caspian Sea and coastal zone. Almaty: Olke, 1995. P.84-90 (in Russian)], [Veselov V.V., Spivak L.F. The basics of the structured modeling of the hydrogeosystems. Almaty: Gylym, 1997, 216p. (in Russian)]. It was believed that surge size in Atyrau is 1.95 m. Duration of the surge is 5 days. The change of the subsoil waters level was predicted for 3 months after surge. The decision method was that. For a 5 days water elevation rised on surge size from 26.84 (1993 year) to 24.89 m. Then the elevation of the water level in the Ural river returned on previous level. The results of the calculations on 1, 3, 5, 6, 8, 10, 15, 20, 30, 95 days after the beginning of surge was analysed. It was established that the short-term surges can not give the essential rise of subsoil waters on the territory of city. They cause drowning a little only for narrow coastal zone on the distance to 100 m from river cut. Practically full return of subsoil waters level to previous state goes on for a 3 month.

Map of forecasted rise of groundwaters level of Atyrau city region for the year 2010

in relation to the yaer 1993 (with Caspian sea water level mark of -26.5 m)
1 - isolines of forecasted level of groundwaters to the 2010 in relation to the year 1993; 2 - model's contours; 3 - Ural river, schematized by the boundary conditions of the first kind; 4 - Atyrau city territory contours

In such a way, retaining phenomenons were caused in subsoil waters in city firstly by self-drowning a little processes at the cost of leakage from water-supply and sewer net of the city watering of green plantings and filtration from the irrigation canals.

In conclusion it is necessary point out the following.

At a later time it is appropriate creation of the detailed models of some parts of the coastal territory that have important role for economy. It is necessary for more authentic estimation and forecasting of the possible rise of the background water level in the Caspian Sea, and also surge phenomenons on subsurface waters.
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