Heather Morning, with her search dog Milly

A mountain expert is warning hillwalkers and climbers to make sure they keep properly hydrated when they head out during summer.

Lack of water can be dangerous, leading to poor performance and decision making, the Mountaineering Council of Scotland’s safety officer said.

And the best indicator is not thirst, but the colour of your pee.

Heather Morning, the council’s mountain safety adviser, said dehydration can lead to a lack of alertness, which can have serious consequences on difficult or exposed ground. She said it can also cause headaches and aching limbs.

For a nation more attuned to keeping water out in our damp climate, it’s easy to overlook the need to drink plenty when in the great outdoors.

Ms Morning said: “It’s important to drink plenty of fluids when hillwalking – especially during the warmer weather in summer.

“As we climb a hill we are sweating and losing fluid – far more than normal. And when you lose more fluid than you take in, it upsets the balance of salt concentration in your body, which then affects many of the body’s functions.

“Common symptoms of dehydration on the hill are thirst, yellow urine, fatigue, dizziness, lack of concentration and headaches.”

She recommends drinking before, during and after a day on the hill, aiming for two litres during a six- to eight-hour day.

“Water is heavy – a litre weighs a kilogramme – but it’s not necessary to carry it all with you,” Ms Morning said. “Water in the Scottish mountains is arguably some of the cleanest in the world, but be sensible.

“Ensure your water source is upstream from the highest habitation and that the water is flowing.

“Using a hydration pack may be useful to encourage drinking little and often rather than having to stop and take a bottle or flask out of your rucksack.

“I am often guilty of being dehydrated on the hill, and my body is very good at telling me the next day, with stiff, sore leg muscles.”