Rules governing use of water resources and operating procedures should be approved individually for each reservoir.In the summer of 2007 during passage of the spring flood, facilities for the distribution of mass information, for example, television, repeatedly attracted the attention of the public to a situation where a number of population centers located in the tail race of the Zeya hydroproject would be partially inundated. Unsubstantiated statements concerning improper actions of operating personnel at the Zeya HPP, and even as though the flooding had been induced by "human hands" were sounded in the reports.Let us point out that the historical maximum flow rate in the area of Zeya, which had been reestablished in the detailed design [1] on the basis of information relative to water levels published in [2], had been attained in 1886 at 16,600 m 3 /sec. The continuous flow rate of 15,200 m 3 /sec at the site of the Zeya HPP on 19 July 2007 occupies second place after the absolute maximum over the entire period of available information (121 years); this is an unusual event. The Zeya hydroproject most likely prevented one of the most damaging floods, which could have occurred on the Zeya River, and in the middle course of the Amur River under modern conditions in the Far East.Let us stress that the reservoir behind the Zeya HPP plays a significant role in preventing and reducing damages sustained from riparian floods: the 0.01% probability that the maximum design flow rate will be exceeded in the Zeya River is reduced by nearly a factor of three, appreciably diminishing the frequency and area of spring floods in the Zeya and Amur Valleys.The purpose of this paper is, however, to inform specialists and journal readers of the fact that it actually occurred, and for whatever the reasons may be, and that we must, in our opinion, strive to render a similar situation prohibitive in the future.Minor flooding had also occurred during passage of the spring flood through the Zeya hydroproject in 2006; we therefore deem it necessary to relate this information to the hydrotechnical community. Basic Terms and Definitions Adopted in the PaperWater Regime -the variation in the water levels and flow rates within the river over time, which exert an influence on the hydrotechnical complex in question;Conditions for Runoff Formation -basic runoff conditions, which determine the formation of maximum flow rates and highest water levels in the rivers;Extent to Which Hydrology Is Studied -existence of hydrological stations and posts, which are operated by the Rosgidromet and other organizations, and are located in the river basin and its tributaries;Maximum Runoff -a conventional term adopted in lieu of the "maximum flow rate" concept during high water in the rivers, the channels of which abut sections designed for water-development works. The assigned probability that the highest water level will be exceeded is defined in terms of the maximum flow rate of water with respect to the hydraulic characteristics of the channel in the form...

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A procedure is proposed for enhancement of the hydrologic safety of entities in the tail races of dams.

A brief characterization of the Amur River Basin and its major tributaries, the operating regimes of the Zeya and Bureya hydroprojects during passage of the 2013 flood, and a list of new hydroprojects, the construction of which is possible for flow regulation and flood control, are presented.

The Atbashi hydroelectric station with an installed capacity of 40,000 kW was put into operation in early 1970; the total capacity of its reservoir is 9.58 million m s, the useful capacity is 4.34 million m 3 at the normal pool level (NPL) of 154 m, and the dead storage level (DSL) is 145 ms The structures of the hydrostation include [i]: a gravel--pebble earth dam with a height of 79 m with a grouting gallery and grout curtain (Fig. !), operating tunnel spillway Qdes = 330 m3/sec, intake and power tunnel d = 5 m, I = 300 m, powerhouse with four units, grouting adits in the rock walls located at two levels ( Fig. 2), access adits, and a diversion tunnel. The hydrostation is located in the high-mountain region of Central Tien Shan on the Atbashi River, a left-bank tributary of the Na~/n River.The region of the hydrostation site has complex toBographic and engineering-geologic conditions: the foundation and bank abutments of the dam are composed of marmorized limestones whose permeability is characterized by permeability coefficient 0.2-0.01 m/day.The numerous fractures in the limestones are mainly of a tectonic origin. The bank release fractures with an open width to 50 cm, usually filled with sand--clay material or calcite, extend tens and hundreds of meters~The developed ancient karst has cavities from several millimeters to tens of meters.The groundwater level is 15-18 m below the water level in the river. The seismicity of the region is intensity 8. The climate is markedly continental: the mean annual air temperature is +2.5~ with an absolute maximum of +34 ~ and minimum of --38 ~ The mean annual discharge of the Atbashi River is 32.8 m3/sec, the sediment load varies from 0.I to 5.8 million m31yr, and the volume of runoff of shuga reaches 5.6 million m3/yr. At the present-day level the minimum storage of the reservoir for daily and weekly regulation needed for the Atbashi hydrostation to eliminate the weekly nonuniformity of the load is 1o7 million m 3. Since the volume of sediment and shuga [spongy ice lumps] far exceeds the indicated quantity, for providing operation of the hydrostation it was necessary to specify --for the first time in our country for a reservoir on a mountain river --deep (more than 40 m) annual flushing with complete drawdown of the reservoir during recession of the flood and brief stopping of the hydrostation.Such flushing was planned in stages with alternation of a partial rise of the water level in the reservoir and discharge of the clarified water for washing out the deposits formed in the lower pool during flushing into the Naryn River (a distance of about 4 km).Periodic deep flushings are supplemented by constant flushings in the su~er and fall by discharging surplus water at the 145-m DSL.For deep flushing, the inlet structure of the operating tunnel spillways has a number of special features (Fig. i): the sill of the radial gate is located 42 m below the NPL and the three-level intake openings, in the event of clogging of the lower opening by sediments, make it possible to flush ...