Abstract. The impact of a hydropower plant (HPP) on the environment, first of all on the riverbed of downstream reach as well as on fish communities is analysed in the paper. Frequent switching on and off of turbines has been determined to be the reason of intensive and long-lasting riverbed scour, also significant reduction of fish communities. Each switching on and off of HPP turbines is found to cause a sudden change of water discharge and level in the downstream reach. Water level suddenly drops down after the turbine switches off. Uplift force of ground water flowing from a riverbed destructs a reinforcing layer of large ground particles formed during the self-lining process. Scour of small particles from the bottom sets in. The riverbed deepens significantly until a new reinforcing layer forms. Suggestions are given to slow down turbine switching within technical possibilities. This simple measure allows to increase the length of a reflux wave, to reduce the speed of water level drop and the length of river reach under the scour danger.
Abstract. This paper presents new ideas about the possibilities to increase the reliability of clay slope stability computation method. Many known methods are proved to give controversial results. The reason for this discrepancy is explained to be the result of assumptions and simplifications introduced into the methods, insufficiently precise estimation of porous water pressure, and the dependency of clay cohesion on a sudden change of compression as well. The method of a modified Boussinesq equation and slices is suggested to compute slope stability in terms of clay cohesion and internal friction determined under unconsolidated-undrained conditions.
This article concerns the influence of water plants on the river flow. It is known that the influence of the plants is rather strong. Colonies of water plants with long afloat culms create considerable forces of resistance to the flow. They reduce flow velocity and increase a stream depth, what often is desirable. Water plants location in a stream is uncontrollable. They appear in not suitable locations of the river and mostly obstruct than help to control the river flow. Water plants and their colonies served for us as a prototype for creation of the flow control system. A method of computation and field tests that enables designing and arranging an artificial water plant system is presented in this article, and it may be used successfully to increase the river flow depth and to improve navigation, free-flow (kinetic) hydropower development and recreation conditions. The suggested system for river flow control is simple, cheap and friendly to the environment.
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