Is Galveston Bay safe for swimming?

  • December 10, 2019
  • News

Summers in South Texas can get hot! It’s no wonder so many people in the Houston-Galveston region choose to cool off with outdoor activities on the water, such as swimming and boating. Galveston Bay Foundation (GBF) often gets asked if the water is safe to swim in, and fortunately, we have the answer!

GBF’s Water Monitoring Team collects valuable water quality data including fecal bacteria concentrations at many nearshore sites around the Bay on a monthly basis. The most recent fecal bacteria concentrations for each location are recorded on GBF’s Bacteria Results Map at

Fecal bacteria (Enterococcus sp.) are commonly used to measure water quality in Galveston Bay because of their tolerance of salt water. These naturally occurring bacteria are found in the gut of birds and mammals, including humans. Exposure to fecal bacteria can cause sickness such as rashes and skin irritation, as well as eye, ear, and respiratory infections. High bacteria levels can lead governmental agencies to issue beach advisories and restrict public access to beaches, bayous, or bays.

Additionally, high concentrations of these bacteria and associated pathogens can accumulate in oysters and other shellfish, making them unsafe to eat, especially if eaten raw. Large areas of Galveston Bay are closed for harvesting shellfish for direct consumption due to elevated concentrations of bacteria.

Luckily, bacteria levels in Galveston Bay are usually safe for swimming. Read on to learn more!

 What causes fecal bacteria to enter Galveston Bay? 
Fecal bacteria are frequently introduced to the Bay system through polluted runoff, malfunctioning wastewater treatment outflow, and even from boater waste discharge. Levels of fecal bacteria generally spike after heavy rain events because major storms wash contamination such as pet waste from our lawns and streets directly into public waterways via the storm drains. Large storms also cause sewage infrastructure malfunctions, such as sanitary sewer overflows, which can lead to an increase in untreated sewage entering our streets and waterways.

Boats with toilets or heads on board also have the potential to contribute to bacteria contamination in Galveston Bay, because even “treated” waste has elevated concentrations of fecal bacteria. This is why it’s illegal to dump untreated waste in the Bay and to dump either treated or untreated waste into Clear Lake.

In the Bay Area, there are currently close to 9,000 registered recreational vessels with heads on board and an average of 821 commercial vessel transits taking place per day. That’s the potential fora lot of waste!

 What factors influence bacteria growth in the environment?  
Once these fecal bacteria have entered our waterways, the length of time they can survive can be impacted by several factors.

Bacteria are destroyed by the UV rays found in sunlight, so they thrive in cloudy or turbid water. Additionally, sand or mud that has been stirred up by wind, waves, or boater activity can reduce water clarity and directly release bacteria from the soil.

Bacteria also grow faster when there is less dissolved oxygen in the water. Low oxygen can occur when temperatures are high or when there is an algal bloom. Algae or plankton blooms are the result of high levels of nutrients in the water. When these blooms occur, much of the oxygen in the water is consumed and the water becomes cloudy. The first evidence of this occurring is often a fish kill, when small fish species die en masse. Perfect conditions for bacteria to grow in!

However, the biggest indicator of high bacteria levels is rainfall. Bacteria levels often spike after a storm, due to polluted runoff from our streets, lawns, and infrastructure malfunctions.

 Infographic: Impacts on Fecal Bacteria 

 How do I know if it is safe to swim? 
Before jumping in with both feet, check out the latest water quality report at Watch out for large amounts of algae floating in the water, or dead fish or wildlife in the area. If the water is very cloudy, or unusually hot or if it has just stormed, think twice before swimming!

Luckily, our bacteria monitoring program has shown that most of the time bacteria levels in Galveston Bay are low enough to be considered safe for swimming.

If you are looking for bacteria advisories on the beach instead of the Bay, visit the Texas Beach Watch website.

 What can I do to decrease bacteria in the Bay? 

This article was written by GBF’s Water Quality Community Engagement Intern, Ted Driscoll