WRRCTR No.98 Water Quality Monitoring: Kaneohe Bay and Selected Watersheds, July to December, 1975

Abstract

A water quality monitoring survey of three drainage subareas in the Kaneohe Bay watershed and selected sites in the bay was conducted between July and December 1975 to ascertain the dry-weather quality baseline. The three drainage subareas were Kaneohe, Waihee, and Waikane. Upstream stations beyond any highly developed areas and downstream stations near the stream mouths were selected in order to obtain some information on the effect of development or land use on water quality. Bay stations were located off the stream mouths, over sewer outfalls in the southern sector, and in the main channels of the bay. The results yielded patterns as expected: poorer quality in the more developed southern and central subareas compared to the northern subarea, poor quality also off the stream mouths and at the sewer outfalls in the bay. The stream monitoring results generally parallel previous studies by the Water Resources Research Center and the Hawaii Environmental Simulation Laboratory. The State Water Quality Standards for Class AA (bay) and 2 (stream) waters were exceeded in the case of nutrients (N and P) and coliform bacteria, but were met in the case of pH and dissolved oxygen. Loading rates, based on mean flow data and parametric concentrations for N and P compared against 1968 data, indicate a two-fold increase for the southern subarea, a lesser increase for the central subarea, and relatively little change for the northern subarea. As expected, the bay water contained but a few parts per trillion of α chlordane, γ-chlordane, dieldrin, and PCP. The stream water samples were generally slightly higher in concentration. DDT, DDD, DDE, lindane, heptachlor, and PCB were not detected. The highest level, although low in parts per trillion of pesticides, was found in stream water draining developed land. Heavy metals, Cd, Cr, Cu, Pb, Hg, Ni, and Zn, were present in bay water in expectedly low background concentrations on the order of a few parts per billion. No gradation in heavy metal concentrations was observed in different parts of the bay. The heavy metal content in the streams was comparable to those in the bay.