No abstract

The continuously increasing needs of the economy for water and the nonuniform distribution of water resources by seasons, in the long-term view and throughout a region, require the creation of reservoirs. The rapid development of branches of the economy in the postwar years caused an especially marked increase in the rate of creation of reservoirs during the past 20-25 years. During this period the number of reservoirs in the world increased threefold and the volume of water stored in them fivefold; in the USSR during this period about 500 reservoirs were created with a total available storage equal to 00% of the available storage of all presently existing reservoirs of the counuy [1].Reservoirs are necessary for irrigation, water supply, water transport, fisheries, power, flood control, satisfying public needs, and recreation for workers. In the future they will be constructed at an cvenhigher rate. since they determine the development of many vitally important branches of the economy.Reservoirs, by virtue of their specifc features and size, exert a considerable effect on the natural and economic conditions of a watercourse and lands adjacent to it. When creating reservoirs, we cannot preserve nature in its original state, since in so doing the most important natural conditions of the watercourse arc changed, among which are: changes of the hydrologic, ice-thermal, and hydrobiological regimes, changes of fishery conditions, surface flooding and rise of the groundwater level (under flooding) of lands, abrasion and erosion, changes in clirnatic conditiom, etc. (Fig. I).Therefore, it would be more correct to say that in creating reservoirs we provide the conditions for the rational use of water and other natural resources, specifying, according to our knowledge of the ecological complex, the measures that will minimize the adverse effects on the environment of creating reservoirs.At present there is a gap between the technical possibilities of man's rational use of natural resources and knowledge about many natural processes being disturbed as a result of man's activities. This lag is apparently related to the fact that the conduct of long and laborious investigations is required when studying natural processes, whereas the use of water resources is based on already existing results of scientific work and implemented technical decisions. Let us consider the measures related to the creation of reservoirs from the point of view of taking into account natural conservation problems and the need for further investigations whose fulfillment would provide in projects a more complete consideration of the effect of reservoirs on the environment.It is known that when designing hydrodevelopments with reservoirs one examines different variants of locating the site and set~ng the normal pool level (NPL) in order to find the variant for which the reservoir being designed would meet the main requirements of the interested branches of the economy and would have the least adverse impact on the established natural complex, For insta...

No abstract

No abstract

According to the information available in the USSR, now in the world there are more than 13000 reservoirs with storage capacity over 1 million m? in service and under construction. The largest ones are illustrated in Table 1. In some countries these storage reservoirs constitute rather a great per cent relative to all the reservoirs of the given country. (Table 2). Lately, such reservoirs have substantially grown in number in many countries of the world, especially in the USSR and USA, what is seen from the chart (Fig.1). In this connection, one can conclude on the great area of some reservoirs (reaching sometimes thousands of square kilometers), on their importance in the balance of the controlled runoff, making up in some countries over 95 per cent and on the intensive increase of their storage capacity beginning from the fifties of the present century. The above said is one of the reasons of greater interest in the action of waves and currents of the shore line showing up most intensively on the largest storage reservoirs. The length of the shore line of the USSR reservoirs is over 40000 km. The length of the erosion shores of storage reservoirs at the hydroelectric projects on the Volga and Dnieper River make up more than 30 per cent of the total shoreline of these reservoirs, while that of the reservoirs on the Kama River - 35 per cent. Most intensively the erosion is going on in the first decades of the operation of the reservoirs. The action of waves on the shore results in formation of the underwater slope with a gradient at which the wave energy is dissipated on the shoal, and the shore erosion slows gradually down until it ceases completely. However, it is rather difficult now to determine the period of the shore formation attenuation process in view of the fact that the problem of distribution of wave energy between all the phenomena taking place here is not properly studied yet and it is hot also clear what width and gradient of the shoal can fully baffle the wave energy and how much time it will take for such a shoal to get formed. The observation carried out on the natural water bodies well prove it.