Fish ladder for passing dams

Abstract

A safe and effective fish ladder assists fish in overcoming dams, especially in the upstream direction. The ladder comprises a series of relatively vertical open pools, which decrease in size in the upstream direction, the pools being conveniently spaced apart a vertical distance which may be easily jumped by the particular fish species of interest. By being arranged relatively vertically, so that the downstream perimeter of one pool is substantially within the downstream perimeter of the pool directly beneath the one pool, the fish ladder does not need to be long and expensive if the dam to overcome is high. Also, by being relatively vertical, the ladder may be conveniently built onto already existing vertical components on the downstream side of a dam, for example, onto the support structure for the discharge flume for downstream migrating fish in the apparatus disclosed in U.S. Pat. No. 5,161,913 (Boylan). Or, by being relatively vertical, the ladder of the present invention may be built even onto the downstream side of the dam itself.

1 . A fish transit system for assisting fish in overcoming a stream obstruction, the fish transit system comprising: 
 an upstream fish transit ladder, comprising: 
 a plurality of open pools, the pools being spaced apart a vertical distance which may be easily jumped by the fish and each pool having an outer perimeter wall adapted to allow water to overflow said outer perimeter wall from pool to pool, said upstream fish transit ladder having an upper end at or near the top of the stream obstruction and a lower end at or near the surface of said stream on the downstream side of the stream obstruction, and  
 water flow from the top end of the upstream fish transit ladder to the bottom end of said ladder via overflow of water from pool to pool over said outer perimeter wall of each pool; and  
   a downstream fish transit flume comprising: 
 a flume upper end at or near the top of said stream obstruction,  
 a flume lower end at or near the surface of said stream on the downstream side of said stream obstruction, and  
 water flow from said the flume upper end to the fume lower end.  
   
   
   
       2 . The fish transit system of  claim 1 , wherein the stream obstruction is a dam.  
   
   
       3 . The fish transit system of  claim 1 , further comprising a support structure supporting both said fish ladder and said fish transit flume.  
   
   
       4 . A fish ladder for assisting fish in overcoming stream obstructions, the fish ladder comprising: 
 a first set of open pools that are spaced apart a vertical distance that may be easily jumped by fish;    wherein each open pool of said first set has an outer perimeter wall that is substantially within the downstream perimeter of the next lower open pool;    wherein each open pool of said first set has a single spout in said outer perimeter wall, so that each pool is adapted to allow water to exit each pool at said single spout and not all along said outer perimeter wall;    wherein said spouts of the open pools are not vertically aligned with each other, and are offset from each other horizontally so that a fish jumping from pool to pool via said spouts swims horizontally in said open pools to move from spout to spout.    
   
   
       5 . A fish ladder as in  claim 4 , wherein said single spout has a width that is substantially shorter than the circumferential length of its respective outer perimeter wall.  
   
   
       6 . A fish ladder as in  claim 4 , wherein said single spout has a width that is substantially shorter than the circumferential length of its respective outer perimeter wall, and the single spout is generally centered in a top edge of its respective outer perimeter wall.  
   
   
       7 . The fish ladder of  claim 4 , wherein said first set has an uppermost open pool, and wherein the fish ladder further comprises a second set of open pools above said first set of open pools, said second set having a lowermost open pool that is larger than, and in fluid communication, with, said uppermost open pool of the first set.  
   
   
       8 . The fish ladder of  claim 4 , wherein the open pools of said first set decrease in size in the ascending direction.  
   
   
       9 . The fish ladder of  claim 7 , further comprising a third set of open pools that is beside said second set of open pools, and that is above, and in liquid communication with, said first set of open pools.  
   
   
       10 . The fish ladder of  claim 4 , wherein said stream obstruction is a dam.  
   
   
       11 . The fish ladder of  claim 4 , wherein said single spout is located at a front edge of each of said open pools.  
   
   
       12 . A fish ladder for assisting fish in overcoming a stream obstruction, the fish ladder comprising: 
 a lower set of open pools spaced apart a vertical distance that may be easily jumped by fish, said lower set of open pools having an uppermost pool;    a transition pool above said lower set of open pools, said transition pool being larger in size than said uppermost pool and having a transition pool spout adapted to allow overflow of water to said uppermost pool;    an upper set of open pools above said transition pool, the open pools of said second set being spaced apart a vertical distance that may be easily jumped by fish, the upper set of open pools having a lowermost pool having a lowermost pool spout adapted to allow overflow of water to said transition pool;    wherein said transition spout is horizontally distanced from said lowermost pool spout so that fish jumping up into said transition pool at said transition pool spout will swim horizontally upstream through said transition pool to reach said lowermost pool spout and will jump up into said lowermost pool via the lowermost pool spout.    
   
   
       13 . The fish ladder of  claim 12 , comprising a second upper set of open pools above said transition pool and beside said upper set of open pools, the second upper set of open pools being in liquid communication with said transition pool via a second upper set spout that is horizontally distanced from said transition pool spout so that some fish jumping up into said transition pool at said transition pool spout will swim horizontally upstream through said transition pool to reach said second upper set water spout and will jump up into said second upper set of open pools via the second upper set water spout, whereby swimming horizontally upstream through said transition pool provides rest for the fish.  
   
   
       14 . The fish ladder of  claim 12 , wherein said stream obstruction is a dam and the fish ladder is attached to and extends up along a downstream surface of the dam.  
   
   
       15 . The fish ladder of  claim 12 , further comprising a downstream fish transit flume comprising: 
 a flume upper end. at or near the top of said stream obstruction,    a flume lower end at or near the surface of said stream on the downstream side of said stream obstruction, and    water flow from said the flume upper end to the fume lower end.  16 . The fish ladder of  claim 15 , wherein said fish ladder and said fish transit flume are supported on a single support structure.