NOTES 
Research in Ground- Water Hydrology in Hawaii 
(Published with the approval of the Director as 
Paper No. 24 in the Journal Series of the Experiment 
Station, Hawaiian Sugar Planters’ Association, Hono- 
lulu, Hawaii.) 
Some 200 billion gallons of water a year are 
drawn directly from ground-water sources for 
the supply of plantations, factories, and homes 
in Hawaii (Davis, 1952, U. S. Geol. Survey, 
Water-Supply Paper 1161: 152). A similar amount 
is drawn indirectly by way of surface streams 
whose low flows, those of maximum value, are 
derived from natural springs. It is not surprising, 
in view of the magnitude of this draft and its 
vital importance to the economy of Hawaii, 
that a considerable amount of study has been 
devoted to the ground-water geology and hy- 
drology of the Hawaiian Islands. 
It is obviously true that the study of geology 
is necessary to the understanding of the hydro- 
logy. Lithology and structure are only geologic 
terms describing the same features as aquifers 
and aquicludes and their geometry. It is also 
true, though perhaps not so obvious, that the 
hydrology can be treated like other geophysical 
and engineering techniques of exploration to 
assist in the development of geologic under- 
standing. 
Hawaii is fortunate, first, in having complete 
coverage by U. S. Geological Survey topo- 
graphic maps on a scale of 1/62,500 with con- 
tour intervals of 50 or 100 feet, based on field 
mapping on scales of 1/31,680 or 1/20,000 with 
contour intervals of 10 or 20 feet. In some areas, 
the older mapping, dating from 1910, is proving 
inadequate, and a current program of remapping 
in greater detail by aerial photographic methods 
is under way; 
Hawaii is fortunate, second, in having the 
results of a survey of the geology of each of 
its islands, largely the result of the work of H. 
T. Stearns of the U. S. Geological Survey and 
Hawaii Division of Hydrography (Stearns, Vak- 
svik, Macdonald, Davis, and Cox, 1935-47, 
Hawaii Div. Hydrog. Bui. 1, 2, 5, 6, 7, 9, H, 
12, Bui. 13 in prep.). In some areas of the 
Islands where the structure is relatively simple 
and the hydrologic problems not severe this 
work may be regarded as sufficient for the un- 
derstanding of the hydrology. In other areas, 
the stringency of the hydrologic problems re- 
quires still more detailed work of the kind done 
by C. K. Wentworth for the Honolulu Board 
of Water Supply (Wentworth, 1951, Geology 
and Ground-Water Resources of the Honolulu- 
Pearl Harbor Area). 
The results of such detailed investigations 
are generally available through the Experiment 
Station of the Hawaiian Sugar Planters’ Asso- 
ciation, the Honolulu Board of Water Supply, 
the outer island waterworks boards, etc. In areas 
of complex geology, much of the extra detail 
may still be provided by the standard methods 
of field geology, although the utility of these 
methods will depend on the state of progress 
of the current program of topographic revision. 
More of the extra detail must come from geo- 
physical and engineering exploration. 
The principal structural elements of a typical 
Hawaiian island are shown in Figure 1. The 
largest element is a shield or dome composed 
predominantly of lava flows, initially of basalt 
but grading in the later flows to andesite, and 
having as a result a thinner-bedded, more por- 
ous, and more permeable interior than exterior. 
These flows were erupted from fissures in linear 
or tripartite rift zones, fissures that were left 
filled with lava, forming dikes. Interbedded with 
the flows are a few ash beds. At the center of 
the dome, there may be a caldera that is either 
partially or completely filled with flows thicker 
and more compact than those on the flanks by 
reason of their ponding. The various islands are 
composed of one to five volcanic domes apiece. 
These domes exist in various stages of erosional 
destruction, from Mauna Loa and Kilauea, still 
active and uneroded, to Kauai, much eroded 
and with much added complexity. After major 
erosion, there may have been a late series of 
eruptions which formed new vents and flows, 
the latter being thicker and more compact than 
the flows of the dome because of the restriction 
230 
