A trick question perhaps?! On World Water Day, our freshwater advisory officer Ewan Lawrie takes a closer look at the answer.

Similar to “how long is a piece of string?”, how you measure and define a body of water can give quite different results. There are a large number of smaller waterbodies in Scotland, particularly peaty pools, which could affect the outcome significantly. A quick poll of people interested in the subject often came up with the answer “lots!”

But if we dive deeper, over the centuries there have been a number of large scale studies of lochs in Scotland, including the many volumes of The Statistical Account of Scotland (1791) by ministers of all the Scottish parishes. The Bathymetrical Survey by Murray and Pullar (1910) described 562 lochs, a truly epic feat that included most of our larger bodies of water.

Also available online is the Standing Waters Database which gives 27,285 records if you filter on Scotland. This does include multiple survey records for some larger lochs, as well as results from around 3,000 sites from the Scottish Loch Survey Project carried out by Scottish Natural Heritage (Now NatureScot) and its predecessor the Nature Conservancy Council between 1983 and 1997. All standing waters on OS maps at a scale of 1:50,000 were identified and lochs were selected for survey based on size, altitude and geology within an area of search. Sites of known conservation value for their freshwater plants were prioritised.

If we turn to Wikipedia, we learn that “It has been estimated that there are at least 31,460 freshwater lochs (including lochans) In Scotland and more than 7,500 in the Western Isles alone.” So there we go, job done. It is certainly quoted in lots of places and the source cited is NatureScot – surely that is reliable enough for anyone! But, how or from where did we come up with this figure?

It almost certainly comes from a chapter by Smith and Lyle in “The Freshwaters of Scotland” based on work for the Institute for Terrestrial Ecology, now, the UK Centre for Ecology and Hydrology (CEH) published in 1979. On the 1:250,000 Scale OS Maps they counted 3,788 lochs. At this scale the lower size limit is about 4ha. From sample counts on larger scale 1:63,360 maps they estimated there are an additional 27,672 lochs giving a total of 31,460.

UK CEH also hosts the UK Lakes Portal, available online. It was originally developed by CEH and University College London in 2004. There are 7,982 lochs under 1ha and 17,637 over 1ha, making a total of 25,619 records in Scotland.

And for all those silently screaming “one, the answer is one!” the Lake of Menteith is not the only lake in Scotland. There are at least six other “lakes” listed on the Standing Waters Database, including Lake Superior in southern Scotland.

No matter how many there are or what they are called, Scotland’s lochs, lakes, lochans and pools are a valuable resource we should celebrate on World Water Day and safeguard for future generations. Find out more: https://www.nature.scot/landscapes-and-habitats/habitat-types/lochs-rivers-and-wetlands/freshwater-lochs