32 



other large islands. It ranges from 31 inches a year in the 

 business center of Honolulu to 21 inches at Ewa and ^^'aianae, 

 all on the south side. On the mauka side of Honolulu City the 

 rainfall ranges from 40 or 50 inches to 90 inches just back of 

 the city. The rainfall reaches 140 or 150 inches in Nuuanu 

 and Manoa valle3^s, but is considerably less on the mountains. 

 On the windward side of the island the rainfall is less than 

 100 inches. It probably does not exceed 100 inches on an 

 average anywhere on the Koolau range. On the ^^ aianae 

 range the rainfall is light. 



"The forest cover is restricted largely to the higher slopes 

 which are now in forest reserves and are being reforested. 

 The lower slopes have been largely denuded by cattle. 



"On account of the nature and arrangement of Oahu's moun- 

 tain ranges there are fewer running streams than on the other 

 large islands. The streams that exist are also smaller, as a 

 rule. Except near Honolulu, most of the streams on the west 

 side of the Koolau mountains are intermittent in flow. For 

 a short time after storms they carry water which is taken into 

 ditches constructed for storm water, but they are practically 

 dry for the greater part of the time. Kaukonahua stream, at 

 A\'ahiawa, is the largest on the west side of Koolau range. 

 All the streams on the east side of Koolau range are short, 

 but they have a good flow. W^aianae is the principal stream 

 from the Waianae mountains. \\'hat Oahu lacks in surface 

 supph^ is largely made up from underground sources. Cane, 

 rice, and taro are extensively irrigated on this island. Pine- 

 apples require no irrigation. 



"Transportation facilities are better on Oahu than on any 

 of the other islands. A belt road crosses the Koolau range 

 and the tableland between the mountain ranges, and a railroad 

 extends almost completely around tiie island. It is thus easier 

 to carry on field operations on this island than on the others." 



SYNOPSIS or THE SURVEY. 



The survey of Oahu, as proposed, would have as its main 

 lines of work llic following: 



1. A topograi)hic survey, resulting in an accurate topo- 

 graphic map, showing contour intervals and all important 

 physiographic features. This w'ork has already been complet- 

 ed, but not made available, by the U. S. .Vrniy Rngincer Corps. 



2. A hydrographic survey, showing geographic and sea- 

 sonal distribution of all waters. This work has been accom- 

 plished by the U. S. Geological Survey, as above referred to. 



3. A geological and soil survey, mapjnng the important 

 geologic formations and soil types. Much data is already 

 available in the publications of various geologists ( for exam- 



