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WRRCTR No.29 Silica in Streams and Ground Water of Hawaii

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Title:WRRCTR No.29 Silica in Streams and Ground Water of Hawaii
Contributors:Davis, Stanley N (instructor)
LC Subject Headings:Groundwater -- Hawaii.
Hydrology -- Hawaii.
Water -- Analysis.
Date Issued:Jan 1969
Publisher:Water Resources Research Center, University of Hawaii at Manoa
Citation:Davis SN. 1969. Silica in streams and ground water of Hawaii. Honolulu (HI): Water Resources Research Center, University of Hawaii at Manoa. WRRC technical report, 29.
Series:WRRC Technical Report
Abstract:Concentrations of silica in natural waters of Hawaii vary from less than 0.2 ppm in rain water to almost 90 ppm in ground water. The acquisition of silica by the water is probably most rapid near the ground surface. Between 1 and 3 ppm will go into solution within a few minutes after rain comes in contact with the rock and soil. Rain water that percolates to the subsurface and eventually becomes groundwater recharge will have from 5 to 20 ppm silica before it reaches high-level dike compartments. The high-level water will continue to dissolve more silica until it has from 15 to 45 ppm silica. Some of the dike water will discharge into streams which in turn recharge the basal-water body and some will leak directly into the basal-water body.
Basal water that may start with 25 to 45 ppm silica will slowly dissolve more silica until it contains from 30 to 60 ppm. Concentrations of more than about 40 ppm appear to be correlated with irrigation return water and in addition may be owing to dissolution of less weathered rocks in
the more arid parts of Oahu as well as the other islands of Hawaii. Rates of silica removal in small watersheds of the high-rainfall portions of the Koolau Range appear to be as much as 8 mg/cm2/yr, which
is more than any other area in the United States. Silica in a relatively soluble form in the basaltic bedrock together with unusually large amounts of water from frequent rains account for the rapid removal of silica in solution. Warm climate and tropical vegetation do not appear to be necessary for the rapid leaching of silica.
Description:U.S. Department of the Interior Grant/Contract No. 14-01-001-1495; B-010-HI
Pages/Duration:vi + 31 pages
Appears in Collections: WRRC Technical Reports

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