2nd International Conference on Rain Water Cistern Systems
St Thomas, Virgin Islands - June, 1984

Section E: Quality Considerations

Paper E.2

Chemical Constituents Of Rainfall At Different Locations In Hawaii

Gordon L. Dugan, Mark S. Tomomitsu & L. Stephen-Lau

Abstract

Five rainfall quality collection sites were established on eastern Oahu, three of which were on an approximate transect up Manoa Valley at distances to 4.8 km (0.68 to 2.98 miles) from the ocean. The median annual rainfall along the transect ranged from 600 mm (23.6 in.) near the coast to 2400 mm (9=.5 in.) farther up the valley. The results of the study clearly indicate that ocean water, based on chloride and sulfate, has a significant infl uence on the quality of rainfall, for areas in close proximity to the ocean The concentration of chlorides, the easiest measured tracer anion, diminishes as the distance from the ocean increases. Volcanic eruptions on the

o f. Hawaii coupled with southern to southeastern winds definitely increases the sulfate/chloride ratio and decreases the pH on Oahu. The study also confirmed the observation from a limited number of previous investigators that organic N is a major portion of the total N of precipitation.

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