Is water safe for a swim? App can tell you

An app designed by the Waterkeeper alliance is expanding to the Charleston area using data from the Department of Health and Environmental Control’s biweekly beach water quality tests and gives users a simplified and location-based interpretation of them.

The difference between polluted water and safe swimming may just be a matter of red and green.

A smartphone app that expanded its coverage into the Charleston area on Thursday would have you think so, anyway.

The app, Swim Guide, pulls water-quality testing data from the S.C. Department of Health and Environmental Control and condenses it into a binary reading — green if the water’s safe to swim in, red if it’s not.

The concept started on Lake Ontario last summer and has since grown across the country under the tutelage of the Waterkeeper Alliance, a collection of local water advocacy groups, said Kristyn Tully, a co-developer of the app.

The service launched an expansion onto the East Coast on Thursday, adding information in the Carolinas, Chesapeake Bay and the Northeast. In Charleston, that includes a total of 27 sites — on Sullivan’s Island, Isle of Palms, Folly Beach, Kiawah Island and Seabrook Island.

DHEC tests those sites twice a month, from May 15 to Oct. 15, for enterococcus bacteria, which indicates whether pathogens are present in the water. Thursday, the app was showing all those sites were safe to swim in. That, said Adam Myrick, a spokesman for DHEC, is because water-quality issues “are few and far between” on Charleston’s beaches.

DHEC doesn’t issue many swimming advisories for the area, he said, because beaches here generally are less urbanized than those on the state’s northern coast. As a result, they’re categorized as a lower priority, and they’re tested less frequently.

Cyrus Buffum, the executive director of Charleston Waterkeeper, agrees that beach water quality generally is safe, and he said his group plans to supplement the app with data it collects from Charleston Harbor.

Waterkeeper will start testing next month at 10 sites where people boat and swim. The group hopes to collect samples at least twice a month, he said, and push that data through to Swim Guide. In the meantime, though, Buffum said that the app still has value, whether or not it has issues to report.

“It’s kind of like house insurance. Why have insurance if my house has never burned down?” Buffum said. “It’s kind of there in the event that something does happen. It’s a tool that can help protect us.”

Reach Thad Moore at 958-7360. w or on Twitter @thadmoore.