After a week of heavy rain, water at many Hawaii beaches is brown with stormwater runoff.
On Monday the state Department of Health Clean Water Branch issued islandwide brown-water advisories for the Big Island and Maui, and advisories continued for several beaches on Kauai.
But there were no current water-quality advisories for Oahu beaches.
“Surprisingly, there are no large areas on Oahu where we need to issue brown-water advisories,” Myron Honda, supervisor of the branch’s monitoring and analysis sections, said Monday after consulting with department staff in the field and lifeguards at some beaches.
Nevertheless, he recommended the public stay out of waters that “appear brown or murky.”
That’s because runoff waters can carry a mix of pollutants from such possible sources as cesspools and sewers, farms, forests and industrial sites, including pesticides, chemicals, dead animals and pathogens, according to the branch’s website.
Brown water also attracts sharks, Honda said.
“A good rule of thumb would be to stay out of the water at least three days after the rain has stopped and we have a good amount of sunshine (which helps kill off pathogenic bacteria),” he suggested, adding that his staff was collecting water samples Monday for routine bacterial testing, and results would be posted on the Clean Water Branch website by about 3 p.m. today.
Sunset Beach resident Tiffany Foyle said she and other local moms didn’t need an advisory to stay out of Waimea Bay on Oahu’s North Shore, where the rain-swollen river has broken through the beach to empty into the sea.
“Haleiwa, especially near Alii Beach, is always chocolate red waters after this many days of rain,” said Foyle.
She and her family have been swimming elsewhere, “where the water is blue and smells like normal.”
But clear blue water can harbor microscopic pollutants, which is why the Clean Water Branch and the nonprofit Surfrider Foundation regularly test beach waters for enterococcus, a bacterium that indicates the presence of fecal pathogens that can cause gastroenteritis and infections.
The U.S. Environmental Protection Agency threshold level for a bacterial advisory is 130 enterococci per 100 milliliters.
The Health Department doesn’t test brown water for enterococcus because it’s presumed to be in there, along with the other nasty runoff stuff, Honda said.
But Surfrider volunteers test for the bacteria whether or not the water is brown, said Christina Comfort, co-chairwoman of Surfrider Oahu’s Blue Water Task Force.
Recently, Comfort compared levels detected in water samples taken from February 2018 to December 2019 at eight beaches along East Oahu’s vast Maunalua Bay.
With only one exception, she found higher levels of the bacteria when rain had occurred within three days prior to sampling than when it hadn’t rained.
The exception, Paiko Beach Restoration Area, showed both counts to be well below threshold, at about 14 bacteria without rain and 8 with rain.
Rain-spiked levels exceeding the EPA standard were found at Black Point (3.8 bacteria without rain, 391 with rain), Waialae Beach Park (49, 206), Aina Haina (20, 463) and Paiko Lagoon (218, 365).
At Kuliouou Stream Mouth, advisory levels were uniformedly exceeded but soared from 332 to 1,029 bacteria after rain.
To track Surfrider’s ongoing test results, visit 808ne.ws/388jbyX.
As winter is Hawaii’s rainy season, Honda urged all oceangoers to sign up to receive email notifications of all beach and water quality advisories at 808ne.ws/35Pcfp1.
And, as rain and wind are expected to continue, according to the National Weather Service, with a high-surf advisory for eastern shores through Thursday, the Honolulu Emergency Services Department advises people to stay away from shorelines and rocky ledges where waves can knock them off, “especially along the Ka Iwi coastline at the Halona Blowhole, Lanai Lookout, Hanauma Bay and Makapuu,” department spokeswoman Shayne Enright said, adding that on Monday there were 11 rescues from Kailua Bay to Hanauma Bay and 1,355 preventive actions taken by lifeguards.