Figure 1. — A low dam with outlet for 

 supplying water to ponds. 



the number of ponds operated from the source of supply. 

 Fortunately, by building proper structures, a suitable 

 volume of water can be obtained. If the stream flow 

 is constant or if the fluctuation in volume is within 

 narrow limits, sufficient water may be obtained by the 

 building of a low dam. 



This dam should be located so that water can be 

 obtained for the ponds by gravity flow. The structure 

 should be of concrete, equipped at one side with an 

 intake box from which the desired amount of water may 

 be obtained for the pond system. Dams of low design 

 provide no obstacle to flood waters and allow debris 

 to pass over readily without obstructing flow. Where 

 the flow is intermittent or becomes considerably reduced 

 during the dry season, it may be necessary to make a 

 larger impoundment by constructing a higher dam ( fig. 1). 



The dam should be anchored in both banks of the 

 stream with bulkheads as high as the banks — this, to 

 protect the banks. The spillway should be built some- 

 what lower than the bulkheads. A concrete apron should 

 be provided to keep the water flowing over the spillway 

 from undercutting the dam. The intake box should be 

 provided with a coarse grating to obstruct large masses 

 of debris, and it should have a slot in which a fine 

 screen is inserted to keep out leaves and materi als that 

 might obstruct the flow of water through the pipe to the 

 pond, and to keep out other fishes. So that the screen 

 may be kept clear of debris without too much difficulty, 

 the screening surface should be large in proportion to 

 the amount of water used. 



Where there is considerable debris in the water, 

 the operator may have di fficulty in keeping the screens 

 clean. In this situation, another type of construction 

 is often used. This involves building a concrete box 

 in the bottom of the stream; the box is slightly raised 

 from the bottom so that it does not become covered with 

 gravel and so that the current continually washes over 

 the surface and carries away leaves and other debris. 



780060 0-48-2 



