Hydraulic and earth engineering – Fluid control – treatment – or containment – Flow control
Reexamination Certificate
1999-11-23
2001-08-14
Will, Thomas B. (Department: 3673)
Hydraulic and earth engineering
Fluid control, treatment, or containment
Flow control
C405S081000, C405S087000, C405S092000, C119S203000, C119S219000, C137S247150, C137S247170
Reexamination Certificate
active
06273639
ABSTRACT:
TECHNICAL FIELD
The invention relates to methods and apparatus for facilitating the migration of fish past dams and other obstacles in waterways. More particularly, it relates to conduits adapted for installation in dams and the like, comprising one or more gate valves for accommodating the up-or downstream migration of fish.
BACKGROUND OF THE INVENTION
Fish ladders have long been used to allow fish to migrate past dams and other obstacles in waterways, in order to permit completion of their life cycle and ensure perpetuation of them as species. The most typical and well known device for allowing fish migration has been the use of artificial ponds stepped between a lower, downstream side of a dam and an upper, upstream side, so arranged that water continuously spilled over the tops of the ponds attracts fish and permits them to swim and jump upstream against a current, as fish are wont to do. Ponds of this type, however, must be specially fabricated at each individual cite, due to the unique geography and geometry of each stream/dam combination, and their construction is materials-intensive, so they are expensive to build. Moreover, because the water spilled over the tops of the ponds must run at a constant rate in order to ensure that any fish which are attracted to the ladder are enabled to swim up it, such ladders can be profligate in their release of water which would otherwise remain reserved behind the dam. This leads to loss of undesirably large amounts of water as a valuable stored resource which might otherwise be put to use for drinking, irrigation, power generation, etc. In addition, stepped-pond ladders must typically be installed at the sides of the stream and dam in which they are located, so that insufficient space is available for the passage of fish at peak season, especially on larger rivers or where large migrations occur.
Other solutions have been offered. Among the most promising are those which provide conduits for the fish to use in passing through the stream obstruction, such as the system described in Norwegian patent 179147. However, even such devices are open to improvements of the type described herein.
For example, U.S. Pat. No. 3,596,468 to Fairbanks provides a conduit-type fish ladder. But flow through the conduit is controlled by valves which have single large openings, so that water under full pressure caused by the head between the upper surface of the water way and the valve itself is allowed to pass when the valve is open. This results in a relatively large, high-pressure stream into which the fish are required to swim. The resultant concentrated, turbulent, high pressure stream is often difficult and sometimes impossible for fish to fight, and many of them die in the struggle, or are so tired by the process that they are swept back to the lower end of the conduit and must try again or give up.
Similarly, the valves provided in U.S. Pat. No. 3,232,060 to Windle provide an option of two relatively large holes or a fully opened valve for the fish to combat. In either case very strong, concentrated flows result which are too powerful for fish to fight.
DISCLOSURE OF THE INVENTION
Accordingly, it is an object of the invention to provide improved method and apparatus for facilitating migration of fish past dams and other barriers in waterways, including valves which provide a relatively reduced fluid flow, with resultant controlled flow rates and relatively uniform turbulence in portions of the fishway downstream from the valves. It is also an object of the invention to provide fishways which provide opportunities for migratory fish to rest on their journey through the fishway, so that a greater number of fish are able to complete migration past the water barrier.
In one aspect the invention provides apparatus for facilitating migration of fish past dams and other barriers in waterways. The apparatus comprises a conduit passing from a downstream side of a water barrier to an upstream side of said barrier, to provide a pathway for migrating fish; at least one flow-controlling valve disposed within the conduit; and at least one actuator for opening said valve in the presence of fish. The invention is suitable for use in facilitating migration past with dams, waterfalls, and any other otherwise difficult or impassable barriers for fish.
Flow controlling valves suitable for use with this aspect of the invention are of many suitable forms. Their primary function is to stop or reduce flow of water from the upstream side to the downstream side of the water barrier through the conduit while closed, so as to reduce flow through the conduit (if necessary) to a rate and pressure at which fish are able to swim into it, and to permit passage of fish through the conduit while open. An important aspect of the function provided by such flow controlling valves is to provide a substantially uniform flow past the valve and through the conduit. As has been mentioned, prior art valves have provided one or sometimes two relatively large openings, which produce relatively concentrated and turbulent flows within the conduit; these currents are difficult for fish to fight. Gate valves comprising three or more substantially uniformly sized and spaced holes, and preferably more, have been found to work satisfactorily. In general, a relatively large number of small holes, substantially uniformly distributed across the valve, have been found to give the best results—the difference between such configurations and valves providing only one or two large holes being compared to the difference between a strong stream from an open hose and the more gentle, uniform stream of the same flow rate issued from a shower head. Any valves adaptable to the uses and purposes described herein will serve. Examples of suitable valves include gate valves and ball valves. Such valves may be adapted for use with the apparatus aspect of the invention by placing holes or openings in the valve body, as described, such that when the valve is placed in the flow-reducing condition—that is, when the gate plate is placed to block the conduit—some relatively reduced, relatively uniformly turbulent flow of water continues to pass through the valve, and then through the conduit (so as, among other purposes, to attract fish to swim upstream through the conduit). Ball valves may be similarly adapted by placing a number of relatively smaller secondary channels through the valve body in a direction more or less perpendicular to that of the primary valve channel, so that when the valve body is turned into a direction in which the primary channel is closed, the smaller or secondary channels are opened and permit a relatively reduced flow of water through the valve; opening of the valve, as in the case of the gate valve, permits passage of fish through the portion of the conduit in which the valve is placed.
Another means for providing continuous flow through the conduit in the apparatus aspect of the invention is to provide one or more bypass conduits around valves present in the main or primary conduit. This alternative is particularly advantageous in embodiments of the invention in which the flow controlling valve fully blocks the primary conduit, as where no holes or secondary channels are provided in gate or ball valves. The use of a number of relatively small bypass conduits provides flow patterns and results similar to those described for gate and ball valves above.
Preferred embodiments of the apparatus aspect of the invention comprise a plurality of flow controlling valves, or valve sets, serially disposed within the primary migration conduit (that is, placed within the conduit in series) so that one or more of the valves or valve sets may be opened without raising the rate of flow of water through the valve to an undesirably high level. For example, having more than one flow controlling valve can permit the opening of one valve to allow passage of fish without causing water to rush through the conduit at the full capacity of the primary conduit, possibly at so high a rate that fish are unable to complete
Eikrem Webjorn
Fjorstad Bjarne
Garrison David L.
Garrison & Associates PS
Hartmann Gary S.
Will Thomas B.
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