Technical Report No. 100
WET-WEATHER WATER QUALITY MONITORING KANEOHE BAY, OAHU, HAWAII
L. Stephen LauReginald, H.F. Young, Stanley K. Konno, Robert J. Oldnall, and Helen H. Lee
August 1976
ABSTRACT
A water quality monitoring survey during the wet-weather seasonal period (January to June 1976) was conducted in the Kaneohe Bay area as part of the U.S. Army, Corps of Engineers Kaneohe Bay Urban Water Resources Study. The survey encompassed three principal drainage subareas, Kaneohe, Waihee, and Waikane, with both upstream and downstream monitoring stations as well as other selected stream and bay sampling points. Both grab sampling and continuous sampling were employed for the stream stations; the latter technique required the use of automatic samplers in order to monitor the runoff from a particular rainfall or storm event.
Mass emissions or stream loadings followed predictable patterns with increases from upstream to downstream stations, higher values in the more urbanized southern areas of the study area, and higher values for this wet-weather period compared to the dry-weather period. In two specific storm events for which data were obtained, the solids load and turbidity peaked before the streamflow hydrograph. Maximum chlorinated hydrocarbon pesticide levels in bay sediments were obtained off-shore from stream mouths, near the urbanized areas.
State water quality standards were exceeded in the case of bay waters for total nitrogen and total phosphorus. The phosphorous standard for most stream stations and the dissolved oxygen standard for both fresh and coastal waters was not exceeded. The total organic content was low except for high runoff events. Insufficient coliform data were obtained for statistical comparison with the state standards.
Chlorinated hydrocarbon pesticides were detected in the ng/l, range for most water samples and two bay samples contained PCB(0. 5 and 0.2 ug/l). Stream samples had higher levels of pesticides than bay samples with a distribution pattern related to degree of urbanization. Heavy metals (Pb, Cu, Zn, Cd, Hg, Cr, Ni) were detected in all bay sediments analyzed.
Urban street sweepings were collected with variations in rate of solids accumulation and concentration of nutrients, heavy metals, and pesticides. The nutrient content was principally organic nitrogen. High lead values were attributed primarily to fallout from automobile exhaust. Dieldrin, a and y chlordane, p,p-DDT, and PCP were found in the ug/l level.