FIG. 19. 



THE IRRIGATION OF THE CANE. 



The privately owned irrigation works in the Hawaiian Islands are 

 unparalleled in other sugar countries, and are indeed comparable with 

 irrigation works developed in connection with any agricultural undertaking 

 elsewhere. Three methods of obtaining water are to be distinguished : 



1 . Pumping from subterranean sources. 



2. Interruption of upland sources and conveyance to the plantations by 

 systems of canals, tunnels, syphons and flumes. 



3. Collection of upland streams in reservoirs. 



The pumps are mostly located at or near sea level as it has been found 

 less expensive to elevate the water through long pipe lines, than to sink shafts 



at a high level and install regular mining 



. ,-J 1 pattern pumps. At the moment of writing 



(1909) the total water pumped daily to an 

 average height of 200 feet in the Hawaiian 

 islands is estimated at 595,000,000 gallons ; 

 the horse power required to effect this 

 service is estimated as 20,000. Of this 

 quantity of water 360,000,000 gallons are pumped in the Pearl Harbour 

 district of the island of Oahu ; 150,000,000 in Central Maui and the balance 

 on the island of Kauai. 



The second method of obtaining water is developed chiefly on the islands 

 of Maui and Kauai, and latterly has been extended to some districts in Hawaii ; 

 altogether the ditches deliver upwards of 600,000,000 gallons daily. 



The total capacity of the reservoirs in the Hawaiian islands is over 

 8,000,000,000 gallons; the largest is that at Wahiawa, on Oahu, holding 

 2,750,000,000 gallons, and hence of the same 

 capacity as that at Craig Goch, one of the 

 reservoirs supplying Birmingham, England. 



O'Shaughnessy 2 estimates that 1,000,000 

 gallons per day per 100 acres is the duty of 

 water in this district ; this is equivalent to 1 34 

 acre-inches in a year, not counting natural rain- 

 fall and evaporation, which may amount to 50 

 inches. In a crop period of 18 months, then, -^ IG - 20< 



22,800 tons of water per acre will produce 50 to 80 tons of cane. He 

 further estimates that owing to leaky ditches, reservoirs and unequal and 

 improper distribution, not more than one-third reaches the area of the cane 

 roots. 



Peru. In Peru cane is entirely dependent upon irrigation, the melted 

 snow of the Andes being the source of water The arrangement of the ditches 

 generally followed is shown in Fig. 19. The regadora, or main canal, leads 

 across the higher part of the field ; from this, by means of a temporary opening, 

 water is brought to the cavesera and is allowed to flow out and run over the 



93 



