312 



the islands of Kauai. Oaliii. Maui and Hawaii. Considering the 

 hniited funds available, a remarkable amount of data of a gen- 

 eral nature was collected and has been published in Water Supply 

 Paper Xo. 318 of the U. S. Geological Survey. While the data 

 ])ublished furnish a considerable amount of general information 

 relative to the water supply of the Territory, it does not go far 

 enough to be of iiigh engineering and economic value to those 

 interested in the actual utilization of the sources of supply of ir- 

 rigation, power and other hydraulic projects. 



The economic utilization of Hawaii's natural water supply is 

 one of the most important factors in the agriculture of the Ter- 

 ritory, and one which calls for intense methods of investigation 

 instead of the superficial or general methods adopted in the past. 

 The investigation of every perennial stream, spring, or other 

 source of w'ater supply should include the following" : 



1. At least 15 years' continuous gauge height records. These 

 records should be obtained by automatic registers which give a 

 continuous record and which cannot make a mistake or falsify 

 records, as is frequently the case in man-read and recorded gauge 

 heights. 



2. Sufficient measurements by weir or current meter to de- 

 velop and maintain rating tables of discharge which may be ap- 

 plied to the recorded gauge heights, and which will give the mean 

 or average discharge for every day in the year, as well as the 

 maximum flood discharge and the minimum discharge. 



3. Sufficient rainfall stations in the catchment areas of the 

 streams to enable the relation of the rainfall to run-off to be 

 worked out, if possible. 



4. A careful study of the topographic and geologic features, 

 the vegetation, forestation and erosive features of the catchment 

 area in reference to possible cooperative work with forestry or 

 other conservation procedure. 



.^. An examination and investigation of all (li\ersions frt^n 

 the stream and its ])resent utilization. 



6. An investigation covering the ]M)ssiblo utilization of any 

 waste water, flood or otherwise, which might be economically 

 utilized by diversion or storage. 



7. An investigation of evaporation losses and of the amount 

 of water utilized in ])lant transpiration and growth, or of. as it is 

 C(jmmonly known, the water duty for various cro])s under various 

 conditions of soil, location, etc. 



'I he first four o])erations are the only ones which strictly aj^ply 

 to hv(lrograi)hic investigation work, but as the hydrographic sur- 

 vey is a necessary i)reliminary step toward the last three investi- 

 gations named, the two i)hases of the work should be kept in view 

 and should be considered in conjunction. 



The first step ncoessar\' for this work i^ ilu- inst.-iUation of the 



