Harlaw Reservoir: Your Complete Guide to Wild Outdoor Swimming in the Pentland Hills
Last updated: May 23, 2026
Quick Answer: Swimming at Harlaw Reservoir in the Pentland Hills Regional Park, near Edinburgh, is a popular wild outdoor swimming spot, though it sits in a legal grey area — Scottish access rights under the Land Reform (Scotland) Act 2003 generally permit responsible access to open water, but Scottish Water, which manages the reservoir, does not officially endorse swimming there. Water temperatures range from around 5°C in winter to roughly 15°C in summer. Go prepared, go safe, and respect the environment.
Key Takeaways 🏊
- Access rights in Scotland are broad, but Harlaw is a working reservoir — swim responsibly and check for any posted notices before entering.
- Water temperature stays cold year-round, typically 5–15°C depending on season.
- A wetsuit is strongly recommended, especially outside of June–August.
- No official changing facilities exist at the water’s edge — bring a changing robe.
- Tow floats and swim buddies are essential safety gear for any open-water swim here.
- The reservoir is roughly 3–4 metres deep in most areas, with deeper sections near the dam.
- Wildlife includes breeding birds, trout, and occasional red kites overhead.
- Harlaw is about 10 miles southwest of Edinburgh city centre, accessible by bus or car.
- Water quality is generally good but can vary — avoid swimming after heavy rainfall.
- Beginners should start in warmer months and never swim alone.
Is Swimming Allowed at Harlaw Reservoir?
Swimming at Harlaw Reservoir is not explicitly banned, but it is not officially permitted or managed by Scottish Water either. Under the Land Reform (Scotland) Act 2003, people in Scotland have a right of responsible access to most land and inland water, which includes open-water swimming. However, this right comes with responsibilities — swimmers must act safely, avoid causing damage, and respect any reasonable restrictions posted by the landowner or water authority.
In practice, wild outdoor swimming at Harlaw has been happening for years and is widely tolerated. That said:
- Check for any signage at the reservoir before entering — restrictions can change.
- Scottish Water’s primary concern is water quality for downstream use, so avoid anything that could contaminate the water (sunscreen, soaps, or swimming near intake structures).
- The Pentland Hills Regional Park authority encourages responsible outdoor recreation broadly, but defers to Scottish Water on reservoir-specific activities.
Bottom line: Go in with awareness. You’re likely fine under Scottish access law, but you swim at your own risk and without lifeguard cover.
How Cold Is the Water at Harlaw Reservoir?
Harlaw Reservoir is cold — sometimes brutally so. As a highland-fed reservoir sitting at roughly 240 metres above sea level in the Pentland Hills, the water temperature rarely climbs above 15°C even in peak summer.
| Month | Estimated Water Temp |
|---|---|
| January–March | 4–6°C |
| April–May | 7–10°C |
| June–August | 11–15°C |
| September–October | 9–12°C |
| November–December | 5–7°C |
Estimates based on typical Scottish upland reservoir conditions. Actual temperatures vary by year and weather patterns.
Cold water shock is a real risk at these temperatures. Even experienced swimmers should enter slowly, control their breathing, and never jump straight in from height. At 5°C, cold incapacitation can set in within minutes.
What Safety Gear Do You Need for Wild Outdoor Swimming Here?
For wild outdoor swimming at Harlaw, the minimum safety kit is a tow float and a swim buddy. Never swim alone at any open-water location, and especially not at an unmonitored reservoir with no lifeguard cover.
Essential gear checklist:
- 🟠 Tow float / dry bag buoy — keeps you visible to boats and other water users, and gives you something to rest on
- 🧊 Wetsuit (3mm minimum in summer, 5mm recommended in cooler months)
- 🧢 Neoprene swim cap — significant heat loss happens through the head in cold water
- 🧤 Neoprene gloves and socks — optional but valuable below 10°C
- 👀 Swim buddy or group — never go alone
- 📱 Charged phone in a waterproof case — for emergencies
- 🏁 Exit plan — know exactly where you’ll get out before you get in
Common mistake: Many first-timers underestimate how quickly cold water drains energy. Plan your swim to be shorter than you think you need — you can always build up over time.
What Kind of Wetsuit Do You Need for Harlaw Reservoir?
A full-length wetsuit of at least 3mm thickness is recommended for summer swims at Harlaw. For spring, autumn, and winter, a 5mm wetsuit is the safer choice. Triathlon-style wetsuits work well for open-water swimming and provide good buoyancy alongside thermal protection.
Choose your wetsuit thickness based on water temperature:
- 15°C and above: 3mm full suit or shorty
- 10–14°C: 4–5mm full suit
- Below 10°C: 5mm full suit plus neoprene cap, gloves, and socks
- Below 7°C: Consider whether swimming is appropriate at all unless you’re experienced in cold-water immersion
Skins swimmers (no wetsuit) do swim at Harlaw, but these are typically acclimatised regulars who have built up cold tolerance gradually over many months. Beginners should not attempt skin swimming here.
How Deep Is Harlaw Reservoir?
Harlaw Reservoir has a variable depth, with most of the swimmable areas ranging from 2–5 metres deep. The deepest sections are near the dam wall, where depth increases significantly and the water is coldest. Swimmers should stay well away from the dam structure itself.
The reservoir covers approximately 22 hectares of open water. Most swimmers stick to the shallower, more accessible eastern and southern banks where entry and exit points are easier to manage.
Best Time of Year to Swim at Harlaw Reservoir
June through August is the best window for wild outdoor swimming at Harlaw. Water temperatures are at their highest (11–15°C), daylight hours are long, and the surrounding Pentland Hills landscape is at its most inviting.
- Spring (April–May): Water is still cold but rising — good for acclimatised swimmers looking to extend their season.
- Summer (June–August): Peak season. Best conditions for beginners and casual swimmers.
- Autumn (September–October): Water cools quickly. Experienced swimmers only after mid-October.
- Winter (November–March): Strictly for cold-water-acclimatised swimmers with proper gear and a support plan.
Early mornings on calm, clear days offer the best experience — flat water, fewer walkers on the path, and the chance to catch mist rising off the Pentlands.
Are There Changing Facilities Near the Water?
There are no dedicated changing facilities at Harlaw Reservoir. The nearest public toilets are in Balerno village, roughly 1.5 miles away. Most swimmers change using a changing robe (dryrobe or similar) at the water’s edge or in their car at the Harlaw car park.
Practical tips:
- Bring a large changing robe — it doubles as a warm layer after your swim.
- Pack a thermos of hot drink. Post-swim rewarming matters.
- Lay a towel or mat in your car boot for a clean change area.
- Arrive with your wetsuit already on if you’re comfortable driving in it.
Water Quality and Health Risks at Harlaw Reservoir
Harlaw Reservoir is a Scottish Water asset, meaning the water is managed for quality as part of the wider water supply network. In general, upland Scottish reservoirs have relatively clean water compared to lowland lakes or rivers, as they receive less agricultural runoff.
However, risks still exist:
- After heavy rainfall, surface runoff can carry bacteria and debris into the reservoir — avoid swimming for 48–72 hours after significant rain.
- Blue-green algae (cyanobacteria) can bloom in warm, still conditions, usually in late summer. These blooms are toxic and look like blue-green paint or scum on the surface. If you see it, do not enter the water.
- Leptospirosis (Weil’s disease) is a bacterial infection spread by rat urine in water. Cover any cuts before swimming and shower promptly afterwards.
- Avoid swallowing water and keep your face out if you have any concerns about current conditions.
Check the Scottish Environment Protection Agency (SEPA) website for any water quality alerts before your visit.
What Wildlife Might You Encounter While Swimming?
The Pentland Hills and Harlaw Reservoir support a surprisingly rich range of wildlife, and encountering it while swimming is one of the real joys of wild outdoor swimming in Scotland.
What you might see:
- Red kites — frequently spotted soaring overhead since their reintroduction to the Pentlands
- Grey herons — often standing motionless at the water’s edge
- Trout — Harlaw is stocked for fishing; you may feel them brushing past
- Dippers and grey wagtails along the inlet streams
- Dragonflies and damselflies in summer months
- Breeding waterfowl including mallards and tufted ducks
Be especially mindful of nesting birds in spring (April–June). Keep noise low and avoid disturbing vegetation at the water’s edge during this period.
How Do Beginners Safely Start Wild Outdoor Swimming?
Beginners should build up cold-water exposure gradually, starting in warmer months and shorter durations. Jumping straight into a Scottish reservoir in April without any cold-water experience is how people get into trouble.
A sensible beginner progression:
- Start in June or July when water is at its warmest.
- Wear a full wetsuit for your first several swims.
- Enter slowly — wade in rather than jumping, and breathe steadily as the cold hits.
- Keep your first swim short — 5–10 minutes maximum.
- Always swim with someone else who knows the location.
- Warm up properly afterwards — change quickly, drink something hot, keep moving.
- Gradually extend duration and move into cooler seasons as your tolerance builds.
Joining a local wild swimming group is one of the best ways to learn safely. Groups like Pentland Wild Swimmers (check local social media for current activity) often meet at Harlaw and welcome newcomers.
How to Get to Harlaw Reservoir from Edinburgh
Harlaw Reservoir is approximately 10 miles southwest of Edinburgh city centre, making it one of the most accessible wild swimming spots from a major Scottish city.
By car:
- Head south on the A70 (Lanark Road) through Currie and into Balerno.
- Follow signs for the Pentland Hills Regional Park.
- The Harlaw car park (off Harlaw Road, Balerno) is the main access point. Parking is free.
- Journey time: roughly 25–35 minutes from central Edinburgh.
By bus:
- Lothian Buses Route 44 runs from Edinburgh city centre to Balerno.
- From Balerno village, it’s a 15–20 minute walk to the reservoir via the Water of Leith path.
On foot or by bike:
- The Water of Leith Walkway connects Edinburgh to Balerno and is a popular cycle/walking route.
- From Balerno, follow the track up to Harlaw — the path is well-marked and easy to follow.
Wild Outdoor Swimming at Harlaw vs. Other Scottish Reservoirs
Harlaw is excellent for accessibility, but it’s worth knowing how it compares to nearby alternatives for wild outdoor swimming in Scotland.
| Location | Distance from Edinburgh | Water Temp (Summer) | Facilities | Atmosphere |
|---|---|---|---|---|
| Harlaw Reservoir | ~10 miles | 11–15°C | None on-site | Peaceful, hills backdrop |
| Threipmuir Reservoir | ~11 miles | 11–15°C | None | Wilder, larger, fewer people |
| Gladhouse Reservoir | ~15 miles | 10–14°C | None | Remote, birdlife-rich |
| Loch Lomond | ~60 miles | 12–16°C | Some at Luss | Iconic, busier in summer |
Choose Harlaw if you want a quick, accessible swim from Edinburgh with a beautiful hill walk attached. Choose Threipmuir (directly adjacent) if you want more space and a wilder feel. Choose Loch Lomond if you want warmer water and a more iconic Scottish setting and don’t mind the drive.
Common Mistakes People Make When Wild Swimming
Even experienced outdoor swimmers make avoidable errors. Here are the most common ones at locations like Harlaw:
- Overestimating ability in cold water — cold water reduces swimming efficiency dramatically. A distance that feels easy in a pool can be exhausting at 10°C.
- Not having a clear exit point — always identify where you’ll get out before you get in.
- Swimming alone — the single biggest risk factor in open-water incidents.
- Ignoring the weather — wind on the water makes swimming harder and colder. Check forecasts.
- Staying in too long — hypothermia can creep up on you. If you feel fine, you may already be affected.
- Not warming up after — post-swim drop in core temperature (“afterdrop”) can happen 20–30 minutes after you exit. Stay wrapped up and keep moving.
- Entering near the dam or outflow structures — these create unpredictable currents and are dangerous.
FAQ: Harlaw Reservoir Wild Swimming
Q: Is Harlaw Reservoir safe for swimming? It can be, with the right preparation. There’s no lifeguard cover, the water is cold, and it’s a working reservoir. Wear a wetsuit, bring a tow float, swim with a buddy, and avoid the dam area.
Q: Can children swim at Harlaw Reservoir? Older children with open-water experience and proper wetsuits can swim here under close adult supervision. The cold water makes it unsuitable for young children or non-swimmers.
Q: Is there a fee to access Harlaw Reservoir? No. Access to the Pentland Hills Regional Park and Harlaw is free. Car parking at the Harlaw car park is also free.
Q: Are dogs allowed near the reservoir? Yes, dogs are welcome in the Pentland Hills Regional Park. Keep them on leads near nesting birds and be mindful of other swimmers.
Q: Can I fish at Harlaw Reservoir? Harlaw is a trout fishery managed by Edinburgh Fly Fishers’ Club. A permit is required to fish. Swimming and fishing can coexist but give anglers space and communicate if sharing the water.
Q: Is blue-green algae a problem at Harlaw? It can occur in late summer during warm, still spells. Always check the water visually before entering and check SEPA’s website for any active alerts.
Q: Do I need a wetsuit for summer swimming at Harlaw? Strongly recommended, even in summer. Water temperatures of 11–15°C feel very cold to most people, and a wetsuit extends safe swim time considerably.
Q: What’s the nearest café or pub to Harlaw Reservoir? Balerno village, about 1.5 miles away, has a small selection of cafés and shops. It’s a perfect post-swim stop.
Q: Is there mobile phone signal at Harlaw? Signal can be patchy in the Pentland Hills. Download offline maps before you go and don’t rely on connectivity for navigation or emergency calls.
Q: What should I do in an emergency at Harlaw? Call 999 and ask for Police Scotland or Ambulance. Give your location as Harlaw Reservoir, Balerno, Pentland Hills. Mountain Rescue covers the Pentlands if needed.
Conclusion: Taking the Plunge at Harlaw
Harlaw Reservoir offers something genuinely special — wild outdoor swimming within striking distance of a capital city, surrounded by one of Scotland’s most accessible hill ranges. The cold, dark water and open skies are a world away from a chlorinated pool, and that contrast is exactly what draws people back again and again.
Actionable next steps:
- Check current conditions — look up SEPA water quality alerts and weather forecasts before any visit.
- Get the right gear — invest in a decent wetsuit, tow float, and changing robe before your first swim.
- Find a swim buddy or group — search for Pentland wild swimming communities on social media.
- Start in summer — plan your first swim for June or July to give yourself the best possible experience.
- Respect the environment — take nothing but memories, leave nothing but footprints, and follow the Scottish Outdoor Access Code.
The Pentlands will reward the prepared swimmer with cold water clarity, red kites overhead, and the particular satisfaction that only comes from swimming somewhere genuinely wild.
Meta Title: Harlaw Reservoir Swimming: Wild Outdoor Swimming Guide 2026
Meta Description: Everything you need to know about wild outdoor swimming at Harlaw Reservoir — safety gear, water temps, access rights, best times, and how to get there from Edinburgh.
Tags: wild outdoor swimming, Harlaw Reservoir, Pentland Hills swimming, Scotland open water swimming, cold water swimming Scotland, Edinburgh wild swimming, reservoir swimming Scotland, wetsuit guide, outdoor swimming safety, Scottish wild swimming spots, Balerno swimming, open water Scotland