Structure and method for facilitating safe downstream passage of migrating fish around hydroelectric projects

Abstract

Structure and method for safe downstream passage of juvenile fish of any species around hydroelectric dam projects using a combination of deeply submerged extended turbine intakes and surface-oriented bypass flows near the dam structure. The turbine intakes are extended upstream from the dam face.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. 119(e) of U.S. Provisional Patent Application Ser. No. 60/873,895 filed Dec. 8, 2006.

BACKGROUND

1. Field of the Invention

The present disclosure relates to structure and method for facilitating safe downstream passage of migrating fish around run-of-the-river hydroelectric projects which include turbine structures, by utilizing natural fish instincts to avoid entrance into the turbines and which promote natural fish movement into safe bypass flows around the dam project.

2. Description of the Prior Art

Hydroelectric projects normally involve a large dam structure with multiple electrical generator turbines which include turbine intakes on the upstream face of the dam to channel water flow through the turbine using the “head” or water pressure from the reservoir on the upstream side of the dam. Many of these hydroelectric dam projects are located on major river systems such as the Snake and the Columbia River systems in the Northwest United States. These streams or rivers are the natural habitat and migration routes for fish, such as but not limited to salmon. The mature fish return to travel upstream to spawn in the river and tributaries of the river system and juvenile fish from hatcheries or natural spawning grounds then instinctively travel downstream to return to ocean habitats. As can well be appreciated, the problem of providing for safe passage, of not only the upstream swimming salmon but downstream migrating juvenile fish, is tremendous. Although many different and even bizarre approaches have been taken, the common approach is that of “juvenile fish attraction” as concerns the downstream migration. To date, none of the efforts to provide safe passage of the juvenile fish around these hydroelectric projects have been satisfactory. Each season a highly significant number of juvenile fish are entrained into the turbine intakes where there are “capture water velocities” and these fish are injured or killed by the turbines or associated hydraulic forces. There is thus a tremendous need for a new approach in terms of method and structures which will allow the juvenile fish to bypass the turbine systems and to enter safe bypass flows from the upper levels of the reservoir, around the dam, through a safe bypass route(s) to be discharged into the project tailrace. The present disclosure provides turbine intake structures for utilizing the natural instincts of the downstream migrating juvenile fish such as salmonids (or other fish species) to provide a safe passage of the fish into a surface bypass flow around the dam. The present concept, instead of utilizing the conventional “juvenile fish attraction” approach, presents a fish guidance philosophy 180° from conventional thinking, presenting fish with “the lesser of evils”.

SUMMARY

Structure and method for downstream passage of juvenile salmonids and other fish species utilizes a combination of deeply submerged extended intakes to hydroelectric projects, i.e. intakes extended upstream from the dam face, and surface oriented bypass flows near the dam structure.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawing FIGURE illustrates the typical profile for a turbine intake on a dam installation.

DETAILED DESCRIPTION

It will be understood that the hydroelectric project schematically shown in the drawing is by way of example and not limitation as a typical system and is not meant to represent any particular project. It will also be understood that the bypass system (not shown) may be any one of many known designs and normally provides a smooth surface flow path near the upstream dam face which is considered to be “conventional” and usually designed to convey 5% to 15% (more or less) of the maximum turbine flow downstream along with the safe passage of the juvenile fish. The bypass normally provides smooth acceleration of transport velocities in a downstream direction and the fish are captured by the accelerating velocities toward the safe bypass route(s). These fish end up safely discharged into the project tailrace. The details of the bypass system, while necessary for safe passage, are not a part of the present guidance system for the migrating juvenile fish.

Referring to the drawing, a schematic cross section of the dam structure is illustrated at 1. The typical turbine intake 2 will normally be provided with a slotted trashrack or the like which is usually cleaned and maintained by a gantry crane (not shown). The reservoir or pool area 4 backed up by the dam provides the hydraulic head for the turbines, the normal pool level being indicated at 6 and an existing reservoir bottom at 7. According to the present system, an extended intake in the nature of a closed conduit 8 extends the turbine intake upstream and will include a lower or floor wall 9 extending along or closely adjacent the reservoir bottom and an inclined upper or ceiling wall 10. The ceiling wall 10 extends from the top of the conventional turbine intake downwardly toward the floor wall 9, forming an intake opening which is submerged as deeply as possible at the bottom of the reservoir. The direction of flow is, of course, as indicated by the arrows in the body of the reservoir 4. In the new intake structure, the conventional trashrack, shown in dotted lines at 3, would be moved to the new position shown at 11. It is of course contemplated that a pier structure 12 of concrete or the like would-be installed to support the relocated trashracks 11 and also a gantry crane 13 provided to operate the trashrack in a conventional manner.

The extended turbine intake 8 may range in length, in an upstream direction, from 20 to 2000 feet from the dam face. The choice of distance for the intake extension will be dependent upon what is “significant” to the targeted juvenile fish species, i.e. the distance the fish would not swim upstream randomly from the face of the dam to the intake extension distance. This choice would thus depend upon the behavior of the targeted fish species. The extended turbine intake opening would be submerged with the tops of the intake openings being as deep as practical considering hydraulic modeling, structural and hydraulic calculations, entrance and friction losses (head losses) and practical experience such as maximum water velocity for intake trashracks. The deepest possible setting for the tops of the turbine intakes or openings would, of course, be the best. The extended intakes 8 would be constructed using cast-in-place concrete, pre-cast concrete sections, metal, or any other suitable materials. It is contemplated that the intake openings 14 would be submerged in the range of 50-100 feet below the surface 6 of the reservoir.

It will be understood, of course, that stop gates for the turbine intakes would remain at the existing location or at any other convenient stop gate location. The fish passage concept includes the consideration that maximum practical width of the turbine intake openings 14 would provide the deepest submergence depth which would be the best for juvenile fish passage reasons.

The present concept and guidance method presents the juvenile fish with the “lesser of evils” for fish passage downstream instead of relying on “juvenile fish attraction” according to presently practiced methods. The fish migrating downstream in groups or schools such as indicated at 16 in the reservoir 4, regardless of their vertical position in the water column, will detect a deep, dark flow movement into the turbine intake opening 14 accompanied by a relatively rapid flow acceleration, turbulence, noise and some vibration of the trashrack structure. Multiple observations of downstream migrating salmonids for example show that juvenile fish will be “repulsed” by these conditions and will instinctively gradually swim away. The initial detection of these adverse conditions by the fish will be at some distance from the intakes, before “capture water velocities” are present. All the fish instincts will be to swim away and this will be easily possible at juvenile fish cruising speeds, the “burst speed” not being necessary. The juvenile fish swimming away from the deep, dark intake openings 14 will volitionally and incrementally move into water volumes that are slowly moving toward the dam face by maintenance of the aforementioned 5% to 15% (more or less) surface-oriented fish passage systems at or near the dam face. In short periods of time, fish avoiding the deep, dark intakes would be surrounded by water heading toward the dam face. Once within these water volumes the fish will be randomly “milling” about, swimming short distances without a clear destination discernible or intended. They will stay within water volumes generally moving slowly toward the dam face and away from the deep turbine intakes 14 upstream.

Bypass flows within 50 feet vertical of water surface, near or at the dam face will maintain passive (i.e. fish milling randomly) juvenile fish movement towards the dam face for all fish avoiding the deep extended intake openings 14. This is so even though the avoidance may be relatively short term. Surface bypass flows of 5% to 15% of maximum turbine flows are initially considered adequate, and this range of flows can only be refined by multiple tests of juvenile fish passage with full-scale facilities. Once at or near the face of the dam the fish will probably refuse any outlet provided (based on past observations), and will mill about randomly for hours, days or weeks. They will mill about across the entire water width and depth accessible near the dam face with no apparent pattern(s) to their movements. It is not expected that they would randomly swim upstream as far as the upstream turbine intake openings 14 because this movement would defy their downstream migration instinct. They will mill about near the dam face as currently observed at many hydroelectric projects. Eventually, their instincts to migrate downstream is expected to overcome their reluctance to enter whatever bypass system is offered, and they enter the bypass system. By reason of instinct, there would not be any other route for downstream passage except the safe route offered near the dam face. The upstream turbine openings 14 would no longer be perceived. Fish then entering the bypass system(s) encounter a smooth acceleration of transport velocities in a downstream direction, and are captured by the accelerating velocities toward the safe bypass route(s). These fish end up discharged safely into the project tailrace. It will be understood, of course, that the bypass facilities may include modified spill gates, normal spill gates, upward or downward acting weir gates, Obermeyer gates, rubber dams, surface bypass spills, orifice passages, ice and trash sluiceways (modified for fish passage), sluice gates, and/or any surface-oriented (within top 50 feet of water column) downstream fish passage systems that have been successfully implemented to date.

Although the present structure, system and method have been described in considerable detail with reference to certain embodiments or method steps, other embodiments and method steps are possible within the purview of this disclosure. Therefore, the spirit or scope of the present application should not be limited to the description of the embodiments contained herein.

Claims

1. In a dam installation for holding a reservoir of water and including at least one turbine with an opening on the upstream face of the dam, a downstream passage system for migrating fish traveling in an instinctive fish passage area in said reservoir, comprising;

an intake conduit extending from said turbine opening in an upstream direction a distance exceeding random reverse upstream travel of migrating fish said conduit terminating in an extended turbine intake remote from the face of the dam and closely adjacent the reservoir bottom beneath the instinctive fish passage area, and

a dam bypass system in the area of the dam creating flow in the reservoir in the area of the dam face to maintain passive fish movement toward the dam face and into the downstream passage system.

2. The downstream passage system of claim 1 wherein;

said intake conduit extends upstream an approximate distance of between 20 to 2000 feet.

3. The downstream passage system of claim 2 wherein said extended intake is located an approximate distance of between 50 to 100 feet below the upper surface of the reservoir.

4. The downstream passage system of claim 3 wherein the bypass flow rate is within approximately 5%-15% of the maximum turbine flow rate.

5. The downstream passage system of claim 4 wherein said bypass system is located within the top 50 feet of the reservoir water column.

6. In a dam installation for holding a reservoir of water in a flowing stream or river course and including a turbine structure with a turbine opening in the upstream face of the dam for channeling water through the turbine, said reservoir providing a hydraulic head for driving said turbine, a safe instinctive downstream passage system providing avoidance of said turbine structure by migrating fish traveling in an instinctive fish passage area located in the upper levels of said stream or river, comprising;

an intake conduit extending from said turbine opening in an upstream direction away from the dam face, said intake conduit having a bottom wall portion located closely adjacent the bottom of said reservoir and a top wall portion downwardly inclined from the upper portion of said turbine opening toward the bottom wall portion and configured to form an extended turbine intake remote from the face of the dam and below said instinctive fish passage area,

said extended intake being located a distance from the upstream dam face that exceeds the observed random reverse upstream travel of migrating fish of a targeted species and deep enough to avoid intake of migrating fish instinctively sensing and seeking to avoid the capture water velocity, turbulence and vibrations associated with the intake,

said extended intake being of maximum width according to hydraulic modeling and dimensioned to provide sufficient flow characteristics according to turbine intake requirements,

a dam bypass system in the upper level of said reservoir in the area of the dam face for guiding fish around the dam and into the project tailrace, said bypass system creating a smooth flow in the reservoir in the area of the dam face to maintain fish movement toward the dam face and into the bypass system for all fish avoiding the deep extended turbine intake, said bypass system presenting the only route for continued instinctive downstream migration travel.

7. The downstream passage system of claim 6 wherein; said intake conduit extends upstream an approximate distance of between 20 to 2000 feet.

8. The downstream passage system of claim 7 wherein said extended intake is located an approximate distance of between 50 to 100 feet below the upper surface of the reservoir.

9. The downstream passage system of claim 8 wherein the bypass flow rate is within approximately 5%-15% of the maximum turbine flow rate.

10. The downstream passage system of claim 9 wherein said bypass system is located within the top 50 feet of the reservoir water column.

11. The downstream passage system of claim 10 wherein the targeted fish are migrating juveniles.

12. The downstream passage system of claim 11 wherein the targeted fish species are salnonids.

13. The downstream passage system of claim 10, including;

a plurality of said turbines, intake conduits and extended turbine intakes.

14. The downstream passage system of claim 13 wherein each said extended turbine intakes include a trashrack across the opening thereof, said system including;

a pier system for supporting said extended turbine intakes, and

a gantry crane system for serving said extended intakes and trash racks.

15. A method for safe downstream passage of migrating fish around a dam project including at least one turbine comprising the steps of;

extending the turbine intake upstream from the dam a distance exceeding observed random reverse upstream travel of migrating fish,

placing said turbine intakes below migrating fish travel in the upper level of the dam reservoir to create deep intake turbulence and vibration whereby migrating fish instinctively avoid captive water velocity flow,

creating a bypass flow to maintain passive fish movement toward the dam face and into a safe downstream passage system.

16. A method for providing safe downstream passage of migrating fish around a dam installation for holding a reservoir of water; said installation including at least one turbine having a turbine intake on the upstream face of the dam and a downstream passage system for migrating fish traveling in an instinctive fish passage area in said reservoir comprising the steps of;

extending said turbine intake in an upstream direction a distance exceeding random reverse upstream travel of migrating fish,

locating said turbine intake adjacent the reservoir bottom beneath the instinctive fish passage area, and

creating a bypass flow in the area of the dam to maintain passive fish movement toward the dam face and into the downstream passage system.

17. The method of claim 16 wherein said extended turbine intake is extended upstream a distance of between 20 to 2000 feet.

18. The method of claim 17 wherein said extended turbine intake is located an approximate distance of between 50 to 100 feet below the surface of the reservoir.

19. The method of claim 18 wherein the bypass flow has a flow rate within approximately 5%-15% of the turbine flow rate.

20. The method of claim 19 wherein said bypass flow is created within the top 50 feet of the reservoir water column.