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Red flag: poor water quality

Despite our best efforts, the water quality in Clevedon Marine Lake is still poor. On July 21st 2021 we took a water sample from the lake that showed a higher level of bacteria than is acceptable for bathing water. We closed the lake and drained the water from the lake so that it could be topped over with fresh water from the sea. But, on July 27th, the sample was still poor against EU bathing water standards.

Why did this happen?

Water quality drops when one of two things happen:

  1. We have a heatwave. Lots of people use the lake and the water temperature goes up.
  2. The water that fills the lake from the Bristol Channel is of poor quality. This happens when storm sewers are allowed to overflow into the sea and when rain washes farm waste off the fields and into the rivers.

In July 2021 both these things happened. First of all, we had a heatwave. Crowds flocked to the marine lake to cool off. Every human body is alive with bacteria that usually lives harmlessly on our bodies, but this washes off in the water. Add sunscreen, bait for crabs and litter, and the amount of new bacteria in the water goes up. On top of this, many feet stir up the mud at the bottom of the lake blocking the sun’s ultra-violet rays that kill bacteria. Also, the water temperature becomes too warm to kill off the bacteria.

After we drained the lake, it topped over with the sea during a pollution warning. Storm Evert brought with it heavy rain. This meant that run-off from the fields polluted the rivers that run into the sea. Water companies also opened their storm overflow sewers releasing sewage into the sea. To find out more about this issue, read here or check out Surfers Against Sewage.

Can I still swim?

The red flags at Clevedon Marine Lake are flying. This means that we don’t recommend using the lake. If you do decide to swim, kayak or paddle there, please take extra care by:

  • hand sanitising your hands as soon as you get out of the water
  • washing your hands as soon as possible
  • having a shower when you get home
  • avoiding putting your head in the water, or if you do, wearing earplugs and goggles.

If you are immuno-compromised or pregnant, please seek medical advice before you swim. Here is a good guide to keeping in good health in open water.

Myth busting water quality

There are lots of myths and rumours on social media about the water quality in Clevedon Marine Lake, so we thought that we’d set the record straight.

Myth #1: The water in Clevedon Marine Lake is dirty

We test the water regularly from April to October. Since we started testing, 80% of the results have been good or excellent. To put that another way, we have had 8 weeks of poor water quality since summer 2018. The lake is usually cleaner than the sea and rivers.

Myth #2: The lake is full of dog poo

‘I heard that when the lake was drained they found a load of dog poo bags at the bottom.’ This is one of the best untruths we saw on Facebook. This didn’t happen. It’s true that bacteria on animals and humans get into the water, which is why we don’t have dogs in or by the lake. But, poor water quality is caused by a combination of four things:

  1. Warmer water temperatures. The lake is quite small and can reach 30 degrees centigrade, which is the perfect temperature for bacteria.
  2. More people in the lake. People bring germs.
  3. Mud getting stirred up. When people stir up the mud in the bottom, it blocks the sun’s UV rays which would naturally kill bacteria.
  4. Big gaps between over-topping tides. The tide must be higher than 12.6 metres to refresh the lake.

Myth #3: The lake’s brown colour is dirt.

Clevedon has the highest tidal range in the world. This means that the silt in the sea never settles. This doesn’t mean that the water’s dirty, but it does cause problems. The mud settles on the floor of the lake where it becomes compacted and stagnant. We drain the lake every March and October for a week to dig out as much mud as we can — this costs £10k a year!

Myth #4: Diet cola kills germs from wild swimming

This doesn’t say much for diet cola, but some swear that it kills bugs from open water. However, it is a good plan to wash after you swim in wild (not treated with chlorine) lakes, pools and the sea. Wash your hands before you eat and have a shower when you get home.

You can help us

Clevedon Marine Lake is run by volunteers. You can support our charity to keep the water clean by:

  • Taking all litter home with you
  • Keeping your dog away from the lake
  • Not using bacon for crab bait
  • Donating so that we can keep on testing the water and draining the lake to clear out the mud