Project Report PR-94-07
Impact of Kawainui Canal on the Recreational Water Quality of Kailua Bay (KB-4)
Lina Ahuna and Roger Fujioka
October 1993
ABSTRACT
The microbiological criteria for recreational water quality have been directed toward the protection of water users from possible microbial pollution which may pose public health hazards. In Hawaii, all streams are classified as recreational waters. Elevated concentrations of indicator bacteria recovered in Oahu’s streams that do not receive sewage or other wastewater effluents and discharges indicate, by present standards, that they are polluted with sewage and pose public health hazards. However, environmental sources of fecal bacteria, such as soils and plants, and fecal sources of non-human origins, such as animals, commonly occur in the environment and appear to be responsible for the elevated concentrations of bacteria found in streams, during both wet and dry weather conditions. High concentrations of bacteria recovered in the upper watershed of Maunawili and the Kawainui Marsh and Canal suggest that bacterial nonpoint source pollution has a significant impact on the recreational water quality of Kailua Bay. Salinity changes at sites compared to the concentrations of fecal indicator bacteria indicate that dilution alone could not account for the reductions in bacterial number; reductions were also affected by other factors such as sunlight. These bacteria in stream recreational waters ultimately impact the ocean receiving waters, suggesting a need for further studies to assess the origins of environmental sources of bacteria, as well as their impact on the health and well-being of the user population.