IRRIGATION IN HAWAII. 



BY WALTER MAXWELL, PH. D., in Bulliton 90, De- 

 partment of Agriculture. 



The precipitation of atmospheric moisture is very uneven and ir- 

 regular over the surface of the earth. There are zones that are marked 

 by annual deluges, and there are vast areas upon which rain rarely 

 falls. These rainless areas are not confined to conditions peculiar to 

 specific latitudes, but are found in the tropical regions of India and 

 Africa, over the wide plateaus of North America, and in other locali- 

 ties having widely varying climatic conditions. 



The regions of small rainfall are very generally distinguished by 

 lands of great natural fertility. This is due largely, on the one hand 

 to the absence of great rains that leach out the elements that feed 

 plants, and on the other hand, to the relative absence of crops, which 

 results from lack of rain. Among the most productive tracts upon 

 the earth to-day are regions that were naturally arid, but which have 

 been rendered productive by irrigation. These tracts include the 

 Punjab and other vast districts of India, the great basin of the Nile in 

 Africa, and large semiarid areas that have more recently been brought 

 under cultivation in the middle and western United States. 



The failure of the natural rainfall to produce crops may be due to 

 the insufficiency of the total precipitation, as in regions in India, 

 Africa, and other lands, where it does not aggregate 10 inches per 

 year; or it may be due to the seasonal distribution, as in other parts 

 of India and Africa, in northern Queensland, and some of the Pacific 

 islands, where a heavy and almost the whole precipitate, takes place 

 within two or three months. In speaking of the agriculture in parts 

 of the Himalayas; Mr. Buckley says: "Where the rainfall varies 

 from 50 to as many as 100 inches in the year, crops grown on the ter- 

 races in the mountains are matured in the dry season by artificial irri- 

 gation.'' In some localities in northern Queensland the annual rainfall 

 reaches and exceeds 100 inches, yet the sugar-cane crop has to linger 

 through an annual arid period which greatly reduces the yield, while 

 upon the Pacific islands of Hawaii, despite the winter rains, many of 

 the most fertile lands would be useless without the prevailing practice 

 of irrigation. Irrigation, consequently, is playing an increasingly 

 important part in modern intensive agriculture 



The history of irrigation covers methods of applying water to 

 '>crops. inducing the crudest efforts of the peasant and the great sys 



