Patent Publication Number: US-2011064522-A1

Title: System and method for reducing the downstream environmental impact of water extracted from a hydraulic dam

Description:
TECHNICAL FIELD 
     The present invention is comprised in the technical field of environmental technologies and, particularly, of the environmental technologies intended to reduce the environmental impact caused by hydraulic dams, with or without hydroelectric use, in a water stream, particularly, a water stream downstream of such dams. 
     BACKGROUND 
     A hydraulic dam refers to a wall manufactured with stone, concrete or loose materials, which is constructed in a ravine or gorge on a river, creek or canal, for the purpose of containing the water in the fluvial bed for its subsequent use. It can be used to increase its level for the purpose of diverting it to pipelines for watering, supply or irrigation, avenue control, etc. or for electric energy production upon transforming the potential energy of the storage into kinetic energy. This kinetic energy will be again transformed into mechanical energy when the force of the water operates a mobile element. When this mechanical energy is used to generate electric energy it is called a hydroelectric power station. 
     The elements of a dam system are:
         The reservoir: it is the volume of water which is retained by the dam.   The basin: it is the part of the valley which, when flooded, contains the dammed water.   The ravine: it is the specific point of the terrain in which the dam is constructed.   The actual dam: which will be in charge of assuring the stability of the construction, withstanding the large thrust caused by the volume of water.       

     On the other hand, it will prevent any filtration of water. 
     In the particular case of hydroelectric power stations, the potential energy of the stored water is used to transform it into kinetic energy, which is in turn transformed into mechanical energy which moves a turbine, generating electric energy. In this type of dam, gates are provided in the wall forming the actual dam, one of which is located in the deepest part, which serves as drainage, and another of which is located at a certain depth (the latter preferably being the maximum possible depth), which serves to take water feeding a turbine, already located downstream of the dam, for electric energy production. 
     Due to the construction of dams in water streams, a series of environmental impacts caused by the latter during the operating phase thereof have been observed on the section of the water stream located downstream, such as:
         Barrier effect of the dam: power stations are barriers to migrations, which affects the fish and other groups linked to fluvial ecosystems. Many fish species perform periodic migrations of certain significance, related to reproduction, use of new food resources and of alternative shelters along the courses of rivers. This problem is solved with the construction of fish ladders.   Modification of the natural downstream bed regime, due to deseasonalization thereof, increasing the cold season period to the detriment of the warm season.   Modification of natural processes of solid material transport, which depends on the flow rate and speed of the water course.   Modifications of the quality of the water causing quality problems, the most important of which occurring in a hydraulic dam are those mentioned below:
           Stratification (temperature): As a consequence of the large volume of dammed water in a dam, in the spring and summer periods, a temperature gradient is generated in said water, which results in different layers of water at different temperature. There is a surface layer at a higher temperature than the layer immediately below it and, evidently, than the deepest layer, the temperature difference between the top and bottom layer being able to reach +13° C. Said thermal gradient does not occur in winter and autumn periods, in which the surface layer of water is colder, close to the temperature existing in the deepest layers.   Degree of oxygenation: This problem results from the stratification occurring in the dammed water, described above, and consists of the fact that the lower layers have a very reduced oxygen content. This is due to the non-existence of sunlight in said deep layers, added to the presence of dead plankton coming from the surface layers, in combination with heterotrophic bacteria.   Turbid water and water with sludge: The viscosity of the water increases as its temperature decreases, thus affecting the sedimentation rate of the particles. Consequently, cold water retains sediments for longer periods than streams of warmer water, as well as to the fact any type of algae which die, various materials, dust, etc., fall to the bottom of the bed.   
               

     The quality parameters mentioned above affect the aquatic life, both the flora and the fauna developing in aquatic ecosystems:
         In relation to the temperature, hydraulic dams lessen, extend, shorten and offset the natural seasonal variation of temperature in the water. These phenomena have an important effect on the mechanisms regulating the emergence of larvae, the laying or phenomena of diapause (stop of the larvae development), variations in the reproductive cycle and in the metabolism of fish, etc.   The degree of oxygenation, more specifically the anoxia in water streams hinders the existence and development of aquatic life.   Turbidity causes loss of habitat for aquatic populations, effects on the respiration and feeding structures of fish and macroinvertebrate species. In the case of water for human consumption, turbidity gives rise to more complex physicochemical water treatments, in addition to the latent risk of causing health problems for the consumers of such water.       

     The prior state of the art has several solutions for mitigating these phenomena. 
     Thus, the patent documents with publication numbers ES2006511 and ES2009862 describe processes for improving the quality of the water downstream of a dam, by means of devices (a sort of cutwaters or combs in the first case, vertical water discharge in the second case) which cause a reoxygenation of the water. But they only affect this factor, reoxygenation, and do not affect the temperatures or the turbidity of the water. 
     The patent document with publication number JP8134877 develops a water purification system, with a water intake system formed by a flexible tube of polymeric material, which can move through the dam. At the upper part of said tube there is a water purifying system which, however, is only intended for water purification. 
     The patent document with publication number SU1671765 describes an intake system for surface water in hydraulic dams which, combined with a deep intake system, allows the water passing downstream of the dam to be surface water mixed with deep water. This document justifies the need to take water coming from both areas to prevent cavitation phenomena, as well as to use the pressure generated by the surface water. However, this document does not describe a system assuring the maintenance of the electric power in a hypothetical hydroelectric power station, nor does it explain the form of operation in the dam in relation to anchors of the system, assembly and disassembly thereof, etc. 
     The patent document with publication number US20070269268 describes a water intake system in dams, describing intake systems for surface water which, after the passage through the turbine or towards the downstream part of the dam, must end in an inlet opening in which an underground gate allows the entrance of water from deep areas. This design is justified to be able to control and regulate the percentage of surface water traversing the dam, as well as to always assure a minimum pressure in the water opening. Although this system considers the intake of surface water and the resolution of the environmental impact caused by the dams, it has the problem of requiring a system of gates to mix surface water with deep water. However, this document also does not describe a system assuring the maintenance of the electric power in a hypothetical hydroelectric power station, nor does it explain the form of operation in the dam in relation to anchors of the system, assembly and disassembly thereof, etc. 
     The patent document with publication number JP10082033 describes an intake system for surface water for dams in which there is a large amount of clays in suspension at the bottom of the dammed water. This document describes an intake system by means of a flexible conduit, with a water inlet opening at its end part. Both the conduit at its end part and the water opening are kept at the same level as the surface water as a result of the action of a floating system. Nevertheless, although the purpose is to feed the gates of the dam with surface water, it is not known if said system affects the electric production, if any, or if it affects the physicochemical conditions of the downstream water. 
     The aforementioned problems have already been observed and studied, and an attempt has been made to solve them by modifying the operating principle of the hydroelectric dam. Thus, patent document with publication number ES2162751 describes a system for electric production from a dam, in which the water feeding the turbine is suctioned from the deep layer of the dam by the Venturi effect, used subsequently. But, as has been stated, it still uses deep water with the environmental drawbacks that this entails, as described above. 
     From the above it is inferred that, in the prior state of the art, there are solutions on the market for reducing the environmental impact of a hydraulic dam. Nevertheless, some of these solutions only improve the oxygenation of the water downstream of the dam by means of devices installed in the dam itself and others, although they take surface water upstream of the dam, require this surface water to be mixed with deep water for a correct operation. With these considered solutions of the state of the art, the environmental impact caused by the dam is not completely eliminated, and at the same time it is not mentioned that the maintenance of the electric power generated in the dam is assured. Furthermore, the different patents mentioned do not describe the different elements or devices necessary for the installation of the system, nor those used to uninstall it (in the event that it is necessary in risk situations). It is also not indicated if it can be applied in any type of dam or only in a specific type. All these issues are developed in the present patent. 
     It was therefore desirable to develop a simple and cost-effective water intake system in hydraulic dams which mitigates the problems of the prior state of the art, allowing the improvement of the quality of the water downstream of a hydraulic dam, without this negatively affecting the electric production of the dams intended for electricity generation, and which at the same time does not consume energy. 
     BRIEF SUMMARY 
     The invention overcomes the drawbacks of the prior state of the art detailed above by means of a system and a method for reducing the downstream environmental impact of water extracted from a hydraulic dam comprising at least one upstream dammed water intake conduit with a water inlet and a water outlet which can be connected to a gate of the retaining wall of a dam. 
     According to the invention, the system is wherein 
     it comprises an intake system for surface water of the upstream dammed water with a floating structure connected to the water inlet and designed to float in the surface water and a water outlet connectable to a feed gate located at an intermediate height of the retaining wall of the dam; 
     the water inlet is located in the surface water to enable a flow of surface water through the water conduit, this inlet preferably having a system for preventing the entrance of foreign bodies which can be jammed in the pipe or in the turbine, as well as also preferably a height regulation system with which it can be regulated in height, so that it is completely or partially submerged in the water; 
     the dammed water conduit is at least one tube with a structure designed to be adapted to various and, preferably, to all the flotation levels of the floating structure without preventing the flow of surface water. 
     The system according to the present invention can be connected, for example, to one or more feed gates connected to a hydraulic power station so that the surface water drives the electricity generating turbine or turbines, and to water drainage systems. 
     The water outlet is preferably connected to the feed gate by means of a connection structure which can comprise a manually or automatically operated frustoconical connection-disconnection hopper. 
     The floating structure can comprise an annular float with a central aperture in which there is arranged a protective grate to prevent the entrance of foreign bodies through the water inlet. Furthermore, the floating structure can further comprise a cleaning system for cleaning the protective grate. This system can be a simple self-cleaning system or it can comprise one or more rotating cleaning blades arranged on the grate and an electric motor driving the cleaning blade. The electric motor can be connected to a photovoltaic power supply assembled in the floating structure. 
     In a first preferred embodiment of the invention, the intake system is a telescopic tube intake system in which the tube is a telescopic tube formed by a plurality of telescopic segments which can be vertically moved in relation to one another, with an upper telescopic segment in which there is located the water inlet and which is connected to the floating structure, and a lower telescopic segment in which there is located the water outlet connectable to the feed gate. The telescopic tube is preferably secured to the retaining wall by means of a plurality of anchors allowing a vertical movement of at least some and preferably all the telescopic segments. 
     This telescopic tube can be provided with a system of guides for lowering and raising it as necessary in each case. 
     In a second preferred embodiment of the invention, the intake system is a flexible tube intake system in which the tube is a flexible tube with a first end in which there is located the water inlet and which is connected to the floating structure and with a second end in which there is located the water outlet and connectable to the feed gate. The flexible tube is preferably designed to adopt a variable radius of curvature depending on the level of the surface water in which the floating structure floats. The flexible tube can thus be made of a polymeric material and can optionally comprise a rigid core to have suitable strength and consistency and to allow a desired radius of curvature. Depending on the depth and on the flow rate which will be drained, the flexible system can be formed by a single tube or by several tubes, without a limit of diameter or of amount of tubes. 
     In this second preferred embodiment, the flexible tube intake system can be furthermore provided with a positioning system comprising at least two cables with respective first and second ends and which pass through respective pulleys anchored in positions horizontally distanced from the retaining wall. The first end of each cable is connected to the floating structure whereas its second end is connected to a counterweight. 
     In the event that the flexible system is formed by several tubes, the latter will be secured to one another at a precise distance so that they work as a single tube. 
     On the other hand, the method for reducing the downstream environmental impact of water extracted from a hydraulic dam is wherein it comprises extracting only surface water and directing the surface water to the feed gate of the retaining wall of the hydraulic dam by means of one or more embodiments of the system defined above. 
     According to what is inferred from the above, the present invention provides a system which can be installed both in existing hydraulic dams and in newly constructed hydraulic dams to improve the quality of the water downstream of the dams and thus minimize the environmental impact of the dams and allow creating suitable conditions for aquatic life, both fauna and flora, since this system will send to the area behind the hydraulic dam, in which there may or may not be electric energy generating turbines, surface water of the upstream area, whereby good physicochemical conditions (temperature, oxygenation, degree of turbidity . . . ) are assured in the area downstream of the dam. Therefore, the present invention allows improving the quality of the water downstream of a hydraulic dam. 
     Therefore, by means of the present invention, similar temperature, oxygenation and turbidity conditions can be assured in the surface water upstream and downstream of the dam, while at the same time, in the event that there is hydroelectric production, the electric power produced does not decrease, in view of the fact that the present invention allows sizing through the design and sizing of the tube or tubes and no type of energy consumption is performed, nor is it necessary to perform substantial constructive modifications in already existing dams or in newly constructed dams, all this with a highly simple structure formed by elements which can be manufactured and assembled with conventional technologies. 
     It can therefore be concluded that the water transferred from upstream to downstream conserves a quality, in relation to temperature, degree of oxygenation and turbidity, similar to the surface water existing upstream of the dam, the characteristics of the downstream ecosystem thus being maintained, with the corresponding reduction of the environmental impact caused by the hydraulic dam in the water stream, due to the improvement of the quality downstream of the dam, i.e., the following is achieved by means of the present invention:
         Preventing the “deseasonalisation” in the temperature of the water, always discharging water at a very similar temperature to that of the stream upstream of the dam,   Preventing the discharge of water with low levels of dissolved oxygen or under anoxia conditions,   Preventing the discharge of sludge by not using water from the depths of the dam,   Preventing the discharge of turbid and eutrophicated water from the depths,       

     all this with a system which can be easily installed and uninstalled in a relatively short time (30 min), in a manual manner by a single person and without providing electric energy, there even being the possibility of providing the system with automatic installing and uninstalling means. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Aspects and embodiments of the invention are described below based on several drawings, in which 
         FIG. 1  shows a side schematic view of a first embodiment of the present invention applied to a hydraulic dam with hydroelectric use; 
         FIG. 2  shows a side schematic view of a second embodiment of the present invention, also applied to a hydraulic dam with hydroelectric use; 
         FIG. 3  is a cross-sectional side schematic view of an embodiment of the upper part of the telescopic tube water intake system of  FIG. 1 ; 
         FIG. 4  is a schematic top plan view of the upper part of the telescopic tube water intake system shown in  FIG. 3 ; 
         FIG. 5  is a cross-sectional side schematic view of an embodiment of the upper part of the flexible tube water intake system of  FIG. 2 ; 
         FIG. 6  is a schematic top plan view of the upper part of the flexible tube water intake system shown in  FIG. 5 ; 
         FIG. 7  is a schematic top plan view of the second embodiment of the invention shown in  FIG. 2 . 
     
    
    
     In these figures there are reference numbers identifying the following elements:
           1  hydraulic dam     2  retaining wall     3  upstream area     4  downstream area     5  surface water     6  drainage gate     7  feed gate     8  feed pipe     9  hydroelectric power station     10  telescopic tube water intake system     11  flexible tube water intake system     12  connection hopper     13  electric motor of the cleaning system     14  cleaning blades     15  float     16  mesh or grate     17  telescopic tube     17   a  water inlet mouth     17   b  water outlet     18  anchor for the telescopic tube     19  flexible tube     19   a  water inlet mouth     19   b  water outlet     20  cable     21  pulley     22  side counterweights       

     DETAILED DESCRIPTION 
       FIG. 1  shows an embodiment of the telescopic tube water intake system— 10 —applied to a conventional hydraulic dam— 1 —which comprises a retaining wall— 2 —retaining dammed water in the upstream area— 3 —of the dam— 1 —, and a hydraulic power station— 9 —located in the downstream area— 4 —of the dam— 1 —. The retaining wall— 2 —has a drainage gate— 6 —located in the deepest area of the upstream area— 3 —, a feed gate— 7 —located between the upper part of the retaining wall— 2 —and the drainage gate— 6 —. The feed gate— 7 —is connected to the hydraulic power station by means of a feed pipe— 8 —, such that when the feed gate— 7 —is opened, the dammed water in the upstream area— 3 —flows through the feed gate— 7 —by the feed pipe— 8 —to the hydraulic power station— 9 —, in which it drives an electricity generating turbine (not shown in the figures), finally reaching the downstream area— 4 —. 
     The telescopic tube water intake system— 10 —comprises a telescopic tube— 17 —formed by telescopic segments, a float— 15 —coupled to the water inlet mouth— 17   a —of the telescopic tube— 17 —and a lower segment with a water outlet— 17   b —coupled to a connection hopper— 12 —which is in turn connected to the feed gate— 7 —of the retaining wall. The telescopic tube— 17 —has a suitable diameter for assuring a sufficient flow of water for feeding the electricity generating turbines of the hydraulic power station— 9 —and is constructed in stainless steel or another material of similar characteristics in terms of strength and durability. To prevent the entrance of air into the telescopic tube— 17 —and, likewise, to allow the entrance of surface water— 5 —, the inlet mouth— 17   a —of the telescopic tube— 17 —is coupled to the float— 15 —such that it remains below the surface of the dammed water. To that end, the telescopic tube— 17  is anchored to the surface of the retaining wall— 2 —facing the upstream area— 3 —by means of anchors— 18 —located at different heights of the retaining wall— 2 —, which anchors— 18 —, in addition to serving as a support system in the event of drainage of the dammed water, allow a vertical movement of the telescopic tube— 17 —such that, when the level of the dammed water rises or falls, and therefore the float— 15 —moves upwards or downwards, the telescopic tube— 17 —can be correspondingly shortened or extended. 
     The anchors— 18 —secure various telescopic elements and form the structure which serves as a guide through which the telescopic segments slide. 
     As can be seen with more detail in  FIGS. 3 and 4 , in the float— 15 —there are assembled a mesh or grate— 16 —preventing the entrance of unwanted objects into the telescopic tube— 17 —, rotating blades— 14 —assembled on the mesh or grate— 16 —, and a motor— 13 —driving the rotating blades— 14 —and fed by photoelectric panels (not shown in the figures). The motor— 13 —and the blades— 14 —form a cleaning system of the grate or mesh— 16 —. 
       FIG. 2  shows an embodiment of the flexible tube water intake system— 11 —applied to a conventional hydraulic dam— 1 —of the same type as that shown in  FIG. 1 . In this embodiment, the flexible tube water intake system— 11 —comprises a curved flexible tube— 19 —made of a polymeric material with a rigid core, to obtain suitable strength and consistency, and to allow a desired radius of curvature. The flexible tube— 19 —is coupled at its water inlet mouth— 19   a —to a float— 15 —and at its water outlet— 19   b —to a connection hopper— 12 —similar to the connection hopper described above with reference to  FIG. 1  in relation with the telescopic tube water intake system— 10 —. The flexible tube— 11 —also has a diameter suitable for assuring a sufficient flow of water for feeding the electricity generating turbines of the hydraulic power station— 9 —. Also in this embodiment, to prevent the entrance of air into the flexible tube— 19 —and, likewise, to allow the entrance of surface water— 5 —, the inlet mouth— 19   a —of the flexible tube— 19 —is coupled to the float— 15 —such that it remains below the surface of the dammed water at the depth which is determined. Likewise and as can be seen with more detail in  FIGS. 5 and 6 , in the float— 15 —coupled to the water inlet mouth of the flexible tube— 19 —there are assembled a mesh or grate— 16 —preventing the entrance of unwanted objects into the telescopic tube— 17 —, rotating blades— 14 —assembled on the mesh or grate— 16 —, and a motor— 13 —driving the rotating blades— 14 —and fed by photoelectric panels (not shown in the figures). The motor— 13 —and the blades— 14 —form a cleaning system for the grate or mesh— 16 —. 
     The flexibility and the radius of curvature of the flexible tube— 19 —are designed such that when the level of the dammed water rises or falls and therefore the float— 15 —moves upwards or downwards, the flexible tube— 19 —adapts its curvature correspondingly so that its inlet mouth— 19   a —can thus be located in the area of the surface water— 5 —of the dammed water in the upstream area— 3 —depending on the level of water in which the float— 15 —is floating. 
     As shown in  FIGS. 2 and 7 , the flexible tube— 19 —is stabilized by means of a positioning system comprising respective cables— 20 —, each joined respectively at one of the ends thereof to the float— 15 —and, at the other end, to respective side counterweights— 22 —, passing through respective pulleys— 21 —anchored distanced from one another in the retaining wall— 2 —. This anchor system minimizes the movement of the flexible tube water intake system, while at the same time, in the event of drainage of the dam— 1 —, it can serve to keep said system— 11 —in the air.