SUGAR IRRIGATION IN HAWAII. 



PROBABLY THE MOST EXPENSIVE SYSTEM 

 IN EXISTENCE, BUT THE COST IS JUSTI- 

 FIED BY THE INCREASED PRODUCTIVITY. 



BY 



BRISTOW ADAMS. 



IN any consideration of irrigation in 

 Hawaii the unique local conditions 

 must be understood thoroughly before 

 the methods in use seem to be justified. 

 On these islands the usual methods of 

 dam and ditch are not in favor for the 

 greater part of the irrigated areas, 

 pumps taking their place and perform- 

 ing most of the work done in producing 

 the phenomenal yields of sugar cane. 



The physiographic contours and the 

 geologic formations of the islands re- 

 quire special treatment from the stand- 

 point of the irrigator. The islands 

 are of volcanic origin, with high moun- 

 tain peaks, formed by successive erup- 

 tions, the more recent flows of lava 

 overlapping the older ones in the form 

 of irregular benches, accompanied by 

 fissures which extend to practically un- 

 known depths. The surface slopes, ex- 

 cept near the sea-level, are abrupt, and 

 the many fissures and folds form effect- 

 ual checks to long transmissions of 

 water except by expensive flumes and 

 pipe lines. Moreover, these fissures and 

 crevices prevent the collection of water 

 and divert streams to underground 

 courses through which they find their 

 way to the sea. The mountain ranges 

 divide the islands into northeast and 

 southwest slopes, irregular and abrupt, 

 but terminating near the sea in table- 

 lands and plateaus capable of a high 

 degree of cultivation. 



The climatic conditions of these two 

 slopes differ greatly. The prevailing 

 moisture-laden trade-winds from the 

 northeast cause a heavy precipitation 

 as they strike the wand ward slopes of 

 the mountains, the annual rainfall in 

 some instances amounting to 250 inches. 

 This causes an abundance of fresh water, 

 which, however, adds to the roughness 



of the slopes and plateaus by washing- 

 out great gullies and ravines ; these do 

 not end in large streams which flow 7 to 

 the sea, as the water sinks through 

 crevices to subterranean passages. Also, 

 hi s excessive rainfall leaches out the 

 soil, carrying off its most valuable con- 

 stituents. A climatic disadvantage is 

 found in the fact that the rainy season 

 is also the cool season of minimum 

 growth, when the crops cannot take full 

 advantage of the rainfall. 



The annual rainfall on the other slope 

 of the mountain is much less and does 

 not exceed 20 or 30 inches, according 

 to the elevation of the land. This is 

 not sufficient to mature crops without 

 the help of irrigation, although the soil 

 is exceedingly rich. A large amount 

 of water is required on account of the 

 slopes, which serve to carry off the rain- 

 fall, and the fissures, w y hich take up great 

 quantities of it. The soil on the less 

 watered portions is much richer than 

 that on the northeast slope, on account 

 of the relative lack of the leaching pro- 

 cess and the relative absence of crops, 

 resulting from less rain. This follows 

 the generic truth that regions of small 

 rainfall are generally of great natural 

 fertility, as, for example, the once arid 

 tracts of the irrigated Punjab of India, 

 the Nile basin, and the areas which are 

 now being brought under cultivation 

 in the western United States. 



Under these conditions it is interest- 

 ing to learn how irrigation has so de- 

 veloped the resources of the islands to 

 the point where such immense crops of 

 sugar are raised, the yield per acre 

 exceeding that of any other region of 

 the globe. There are many difficulties 

 to be surmounted, and success has at- 

 tended only the use of large capital and 



