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Management Experiences in Eastern and Central Europe

The case of River Volga: environmental role of a chain of reservoirs.

In Russia, 41 of the largest reservoirs have a total volume of 1,200 km3, or 25% of the country’s water supply. Bratsk reservoir is the third largest in the world by volume. The Volga River system, with its largest tributary, the Kama, have been converted into a cascade of twelve major reservoirs.

The basin of the River Volga is the economic center of the Russian Federation. The 12 major reservoirs of the Bolza-Kama Cascade retain 174 km3 of water. Currently, over 65 cities with a total population of up to 15 million are situated on the shores of Volga and Kama rivers. The reservoirs are the main source of the citiesEwater supply.

A comparison of the average values of phytoplankton biomass in different parts of the Volga, before and after construction of the reservoirs, has demonstrated that phytoplankton concentrations have decreased by half, in spite of the growth of the human population and a tripling of the phosphorus load. However, the mean yearly total phosphorus concentration in the Volga near the city of Ostrakhan in the river's delta remained almost unchanged, thanks to the high phosphorus retention capacity of the reservoirs. The average water retention time increased from about 20 days to 2.5 years.

In spite of increasing phosphorus loads, the water quality of the Volga and Kama rivers is about an order of magnitude better than that of two major western European rivers, the Danube and Rhine. The difference is mostly due to the decrease in the nutrient concentration along the chain of reservoirs.

The case of Balaton Lake: management of a shallow lake with the use of a pre-reservoir.

Balaton is a shallow, eutrophic lake in Hungary; its area is 600 km2. In summer, the population of holiday visitors reaches one million, with a corresponding increase in the flow of nutrients to the lake. Intensive agriculture also is source of nutrients as are the lake sediments, which are easily stirred by the wind. A shallow wetland, Kis-Balaton used to accumulate the nutrients carried by the River Zala, the main tributary of the lake. Due to an ill-informed decision, the Kis-Balaton was drained and the River Zala was channelled through to the main lake. This lead to increased eutrophication of Lake Balaton.

The Kis-Balaton is now being restored. In addition, other activities are expected to reduce eutrophication in the lake. These programs, including domestic sewage diversion, chemical removal of phosphorus, watershed management, selected based on their cost benefit ratio, are intended to reduce the availability of biologically available phosphorus by about 50%.

Lessons learned in central and eastern Europe

In central and eastern Europe, integrated management of eutrophication has been rather limited and technological solutions have predominated. It may be expected that centrally planned economies would be inclined to integrated management of complex water resources, but they were not. The strategy of large reservoir management was based on a system of allocation among prioritized users with energy production first, followed by communal water supply, irrigation, fisheries and navigation. The management of the reservoirs was not explicitly intended to include eutrophication mitigation, and the high phosphorus retention capacity of the reservoirs was inadvertent.

The understanding of eutrophication processes in eastern and central Europe may be used for the design of poly-sectional reservoirs as described in IETC’s Technical Publication Series number 11 (pages 299-302 and Fig.7.4). According to the design, the upper, shallow part of the reservoir is cut off from the main body of water by a low dam with the gates in it. The gates would regulate an optimal water regime in both parts of the reservoir and in this way control the eutrophication in an integrated way.

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