214 



Division of Hydrography 



Honolulu, Hawaii, April 18, 1916. 



Board of Commissioners of Agriculture and Forestry, Hono- 

 lulu, T. H. 



Gentlemen : — The following report of operations of the Di- 

 vision of Hydrography during March, 1916, is submitted : 



WEATHER CONDITIONS. 



The rainfall during the month was generally light, except on 

 Hawaii, and on all other islands streams and ditches are begin- 

 ning to show depletion. Crops on portions of Kauai have begun 

 to show the effects of dry weather. 



WAIAHOLE TUNNEL DISCHARGE. 



On March 20 fifteen million gallons per day were flowing from 

 the south, or Waiawa, portal, and 1.8 million gallons per day 

 from the north portal. Of the discharge at the south portal, five 

 million gallons per day were flowing from the government end of 

 the tunnel — making ten million gallons per day being developed 

 in that part of the tunnel under Bishop Estate land and about 

 seven million gallons per day in the government end of the tunnel. 



On March 28 a Gurley continuous-record gaging station was 

 established, at the expense of the Waiahole Water Company, in 

 the tunnel at a point directly under the boundary between the 

 government and Bishop Estate lands, about 1750 feet from the 

 north portal. 



A large chamber in which the instrument is sheltered has been 

 excavated at this point and connection made by ladder to the old 

 ''R" tunnel which was originally driven to intercept ground 

 water from the main tunnel, and vv^hich is now dry. "R" tunnel 

 will be used as a means of ingress and egress to the station. 



For about 100 feet above and 25 feet below the station, the 

 tunnel has been lined with masonry and cement plastered to form 

 a smooth rectangular section, through which the water will flow 

 smoothly and without turbulence. A bridge has been built over 

 the lower end of this section, from which velocity and cross-sec- 

 tional area measurements will be made, while the water-stage 

 recorder wnll keep a continuous record of surface fluctuations. 

 The chamber will be lighted with two large gasoline lamps. 



It is estimated that continuous records of the discharge at this 

 point will be obtained within a limiting error of two per cent. 



