Reservoirs and quarries: why most say no, and the ones that say yes

On a hot day a reservoir or a flooded quarry can look like the best swim for miles. Many have a sign saying no swimming, and plenty of people wonder whether it's just a landowner being cautious. The law on access isn't always clear. But the hazards behind most of those signs are real, and they're different from a natural lake. This guide covers those hazards, and where you can swim in a former quarry that's run as a managed venue.

Why reservoirs say no

A reservoir is working infrastructure first. Yorkshire Water says its reservoirs are operational and supply water to be treated, and it doesn't allow swimming in them. Its reasons:

• Cold. It says the water is at a very low temperature all year round, and that cold water shock can kill.
• Depth. Reservoirs are deep.
• Currents. It warns of strong undercurrents where water is continually drawn into large submerged pipes, and of machinery in the water.
• Algae. Blue-green algae can cause rashes on the skin and severe illness if swallowed.

United Utilities says reservoirs aren't the place for swimming or paddleboarding, even on the warmest days, and has a no-swimming policy at most of its sites. It adds two more: deep water and steep sides that make it hard to get out, and remote locations where emergency services can struggle to help. United Utilities also points out that there's no lifeguard to help at a reservoir.

The Outdoor Swimming Society (OSS) takes a different view on temperature. It argues that reservoirs warm up in summer like other water. But it agrees that in summer the warm top layer may be shallow, with colder water below. There's more on that in why big, deep lakes stay cold below the surface. The OSS is also clear that the dangers around dam walls, towers and spillways are very real. See inlets and outlets for how those work.

The access question

The OSS explains that water companies usually own reservoirs and have a duty to provide public access for recreation, but in practice most have a no-swimming rule. It argues for better access, and suggests that more truthful signs, with information about the specific risks, might get more people to follow them. Yorkshire Water allows water sports only where a club or organisation has an agreement in place.

The law differs across the UK. The OSS explains that in Scotland swimmers have a statutory right of responsible access to most land and inland water. In England and Wales it's less clear and more restrictive.

Quarries: deep, cold, and often hiding something

The OSS describes flooded quarries as behaving much like lakes. They warm in summer, and deeper ones may form layers, with warm water on top and cooler water beneath. Those cold layers can cause cold water shock in people who jump in, and cold incapacitation in swimmers who aren't prepared.

What sets quarries apart is what's left from the working site:

• Steep sides. The OSS says stone quarries can have steep sides or drop sharply away from shallow beaches, and there may be few easy places to get in and out. RoSPA notes that in former quarry workings and clay pits, side slopes can change suddenly.
• Unstable edges. Silica banks can collapse, and former stone quarries can have large rockfalls.
• Things under the water. The OSS lists rocks, cars, old bikes and machinery among the underwater hazards.
• Pollution. Some quarries have unusually high pH, which the OSS says can irritate or burn skin. It suggests finding out what was mined on the site.
• Remoteness. Remote quarries may have no phone signal and can be hard for emergency services to reach.

Don't jump

RoSPA's definition of tombstoning includes jumping into a lake, quarry or reservoir, and it warns that hitting a rock or other object below the surface can cause serious injury. The OSS says not to jump or dive unless you've thoroughly checked the area first. See cold water shock for what the cold does to your breathing.

The ones that say yes

Not every quarry is closed. The OSS notes that some have been turned into managed open water lakes, or the centrepiece of holiday villages. If you want to swim in a former quarry, a managed venue is the place to start.

The RLSS recommends swimming at a lifeguarded, recognised venue. It points to Beyond Swim, an accreditation scheme for open water venues created by Triathlon England and supported by Swim England and RLSS UK. Venues are checked on permissions, insurance, risk assessments, operating procedures, emergency action plans and staff qualifications, at two levels: self-declared, or endorsed after Beyond Swim has verified the documents.

When you book, ask what safety cover there is and where to get in and out. Check whether there's a designated swim area and a designated swim time, and take care if you swim outside either. There's more in lifeguards, flags and designated swim areas.

If someone gets into trouble

If you're in the water and in trouble, the RLSS advice is Float to Live: stop thrashing, lie back, get your breathing under control, then think about getting out.

If you see someone else in trouble at a reservoir or quarry in the UK, the RLSS says to call 999 and ask for the Fire Service, look for rescue equipment, throw something that floats, and not to go in yourself. There's more in who to call.

For everything else to think about before a swim in any lake, see safe lake swimming: the complete guide.

Sources

1. Yorkshire Water, Visitor safety
2. United Utilities, Stay safe at our reservoirs
3. United Utilities, The cold that can kill: a GP speaks
4. Outdoor Swimming Society, Understanding Reservoirs
5. Outdoor Swimming Society, Understanding Flooded Quarries
6. Outdoor Swimming Society, Is It Legal?
7. RoSPA, Tombstoning
8. RoSPA, Lake and pond safety
9. Royal Life Saving Society UK, Open Water Swimming Venues and Safety
10. Royal Life Saving Society UK, Top Recommendations for Safer Open Water Swimming

This guide is general information, not a substitute for local knowledge or training. Conditions change: check them on the day, and if in doubt, don't go in. Images on the blog are illustrations, not pictures of specific spots.