IT is the feature that has done more to shape the physical and human geography of Scotland down the millennia than most others, yet very few even know where the country's watershed is to be found.

On one side of it, lochs, burns and rivers flow westwards to drain into the Atlantic Ocean, while on the other they head eastwards to the North Sea.

Now a leading authority is calling for special protection and recognition for the near-750 mile line which meanders across the map from the Borders, south of Jedburgh, to Duncansby Head, the north-east tip of Caithness.

It all began 12 years ago. Peter Wright, 67, fancied doing a long challenging walk, one that had not been often done before.

"I thought to myself, Scotland must have a watershed," he said.

He could only find two historical references, one in a gazetteer published in 1884 which simply said its northern terminus was at Duncansby Head, the other from was an atlas in 1912, which implied Scotland was divided by the watershed.

Apart from that there was one book published 25 years ago about walking the watershed.

Mr Wright said: "It was an excellent book about mountaineering and hillwalking, but I disagreed with its conclusion that the watershed ended at Cape Wrath, the north-west point of Scotland, rather than at Duncansby Head."

So in 2005 he set out to discover the truth. He said: "It took me 64 days of walking over a nine-month period. I was out for a long weekend, a week and then up to a fortnight at a time. I had to fit it round my job as manager of the Duke of Edinburgh Award scheme in the Edinburgh area."

He says his fascination with physical geography had stayed with him since he left school in Dublin at just 14. He was to go to Newbattle Abbey College in Dalkeith in 1968 as an adult student, which he described as life-changing.

It had opened the door to his ambition to train as a youth worker at Moray House College in Edinburgh. His chosen career gave him plenty of opportunity to explore Scotland's countryside, but the watershed was the most ambitious challenge.

He found only one settlement along its route, the new town of Cumbernauld.

"I must say the watershed-eyes's view of the town is very green and redeeming," he said.

"I found I was never more than 100 paces from greenery and was always linking up with woodland or old hedgerows. Meanwhile there are only around 20 houses built on the entire length of the watershed itself. It is a big, big emptiness."

Mr Wright said the actual line varied greatly. "It is very narrow on the South Glen Shiel Ridge near Kyle of Lochalsh, where it is only a yard wide. But it is a bit more ponderous in the likes of the Flow Country of Caithness and Sutherland, where it takes a while to make up its mind. In fact in some places it would be hard to plot it over half a kilometre."

He wrote three books about the watershed. Ribbon of Wildness was published in 2010, Walking with Wildness in 2012, and Nature's Peace in 2013.

"The Royal Scottish Geographical Society endorsed Ribbon of Wildness as being the first definitive description of the watershed. I find that amazing given that I am a rank amateur. If we went to North America they know exactly where their Pacific/Atlantic watershed is and celebrate and promote it as 'The Great Divide'. But here it is very different.

"Our watershed been where it is since the end of the last Ice Age and has not only shaped the landscape but has influenced where people settled. Yet there is no real recognition."

Mr Wright says as we approach the centenary of the death on Christmas Eve of Scots- born wilderness champion John Muir, there should be a debate about how to recognise Scotland's watershed. "One idea I had was a chain of Unesco biosphere reserves," he said. "But I am open to any other idea. I just think we should start talking about it."