( 12 ) 



these canals are head-sluices, where the amount of water 

 entering can be regulated in accordance with local require- 

 ments, or entirely cut off if necessary. 



XVIII. Irrigation weirs constructed simply for irriga- 



tion are those in which boat-traffic 



Simple irrigation weirs. j i i i i 



cannot be also carried on, due to one 



or more vertical falls existing which are too great to permit 

 such. These falls, which are sufficient to prevent traffic, 

 are mostly also sufficient to entirely obstruct fish, which have 

 once descended over them, from ever re-ascending. These 

 canals almost invariably have a high fa]l near their com- 

 mencement, whilst below all overflows, and due to the action 

 of descending water, are holes of a larger or smaller size in 

 their bed, and being well adapted for feeding in, here large 

 fish live and thrive so long as they are permitted. The 

 further the distance from the canal head, and as the amount 

 and rapidity of the flow of water decreases, the falls are 

 usually less and these holes are smaller; still, even there they 

 are present, but are not so suitable for providing food for 

 large fish. It will thus be seen that these canals form large 

 receptacles which may be turned into traps for all fish which 

 once obtain an ingress, unless there are tanks connected with 

 them into which they could retire when the water is cut off 

 and they become dried, or else that the holes in their beds 

 retain a sufficient supply during these periods, so that the 

 fish may remain in safety until the water is re-admitted. 

 For at certain times every year, it becomes necessary to dry 

 off these canals to enable the engineer officers to ascertain 

 what repairs are necessary, and unless the fish have a safe 

 place to resort to they might be easily taken. But, unfor- 

 tunately, in some canals it is, or has been, the custom to allow 

 the employes to kill all the fish at this period, and thus a 

 simple irrigation canal becomes a vast trap for destroying 

 fish. (See para. 12, p. v.) 



XIX. In canals which are constructed for both irri- 

 irrigation and navigation gation and navigation, there are lochs 



cauals - at every fall, that boats may be 



admitted and floated up to a higher level. At these lochs 

 I have observed that fish can obtain a passage up or down 

 stream, so they will not be further alluded to. 



XX. None of these canals contain gratings or other 

 HOW fish are carried into appliances ^ at their commencement 



irrigating cauais, and how they for preventing the ingress of fish, and 



peri* bom want of water. &n offi(}ial iQ ^ North . WeS tem 



Provinces (para. 334) observes upon Laving personally 



