Why a tarn pitch is worth the extra mile

An upland tarn gives you water at arm's length, a clean horizon and the sort of stillness that only arrives once the day walkers have gone home. In the Lake District, Snowdonia, the Cairngorms and the Cheviots there are hundreds of them, from small peaty pools between hummocks to sizeable sheets of water tucked under crags. What makes them wonderful also makes them awkward to camp beside: they sit in hollows, they collect cold air, and the ground around them is often either sodden or made of boulders. A little judgement before you unroll anything will decide whether you wake up rested or spend the night sliding downhill into a puddle.

Read the ground before you unroll anything

Walk your chosen area first, even in the last of the light. You are looking for a patch that is level, firm, about a metre longer and wider than your tent, and slightly raised above everything around it. Kneel down and press a palm into the surface. If water rises around your fingers, keep moving.

• Short, springy grass is usually the best sign: well rooted, reasonably dry, and comfortable to sleep on.
• Tussock grass and heather hide ankle-turning gaps and hold damp underneath. Flattening it also damages it badly, so avoid it even where it looks tempting.
• Sphagnum moss, cotton grass and bog asphodel all say "wet" loudly. Give them a wide berth.
• Bare peat or black, cracked earth is usually eroded and often protected by fragile vegetation. Do not add to the damage.
• Granite slabs and shingle drain beautifully but will not take pegs. Useful in foul weather if you are happy to use rocks.

Drainage: where the water wants to go

Tarns are natural sumps. Water arrives from the slopes, sits in the basin and leaves by an outflow, and the ground between those two points is likely to be wet year round. Pitch on the shoulder of a rise, well above the high-water line, and never in a dip that looks like a shallow channel. Even a few centimetres of elevation matters when rain arrives at two in the morning.

Avoid the obvious tempting spots: the flat grassy apron at the inflow, the level ground beside the outflow, and anything within a couple of metres of the shore, where wave splash, spray and heavy foot traffic combine. If the tarn has a stone dam or a weir, treat the ground below it with suspicion.

Porches matter too. Pitch so the door faces away from the prevailing wind and you can cook without kneeling in mud, and dig no trenches. If the site needs drainage work, it is the wrong site.

Wind, fetch and the shape of the land

Upland basins are wind machines. Air accelerates through cols and gullies, and a tarn sitting in a bowl will funnel whatever is blowing into a steadier, stronger stream than the map suggests. Look for natural shelter that does not put you under anything: a rock outcrop on the windward side, a wall of boulders, the lee of a low ridge. Bear in mind that wind shifts overnight, so a pitch that is calm at dusk can catch the full blast by midnight.

Do not camp under lone trees, dead trees, or crags where loose rock might come down. In Britain those trees are often the only ones for miles, and they drop limbs impressively. Tarns also gather cold air at night, so a hollow that feels sheltered may be several degrees colder than the slope above it, with mist forming by dawn. A spot a short way up the hillside is often drier, warmer and breezier than the shore itself — and better for midges, which hunt in still, damp air.

Bothies, rights and pitching with courtesy

Where a bothy sits beside a tarn, the etiquette is straightforward. Bothies are for shelter, not for pitching your tent inside or draping wet kit over every surface. Camp outside if the place is busy, keep the fire out of the hearth unless there is a clear, established fireplace, and carry out everything you brought, including the things other people left. Never rely on a bothy being empty, and never treat one as a guaranteed fallback in bad weather.

On access, Scotland gives you a legal right to wild camp responsibly under access legislation. In England and Wales there is no general right, though some areas tolerate lightweight, one-night, leave-no-trace camping. Dartmoor operates a restricted, bookable arrangement rather than the old open presumption. If in doubt, ask the landowner or check the relevant national park's current position before you travel.

Small details that make a dry, quiet night

• Pitch late and leave early. Arrive after the day's walkers, gone before the morning's.
• Carry a few extra pegs and long ones for stony ground; rocks make fine anchors if you wrap them carefully.
• Treat tarn water by filter or boil. Livestock graze high ground, and blue-green algae can appear in warm spells.
• Keep groups small and spread out. Two tents in one spot leave twice the mark of one.
• Take a bearing and know your escape route before dark. Cloud can swallow a tarn shore very quickly.

Choose the pitch with the same care you would give a route in winter, and an upland tarn becomes one of the finest places in Britain to spend a night: water at hand, a dark sky, and nothing between you and the weather but a thin sheet of nylon.