Scotland is fortunate in being very richly endowed with natural fresh waters in the form of numerous lochs and rivers. These constitute on the one hand an attractive feature of the landscape and on the other a major resource for industry and recreation. Thus there are about 3800 lochs over4 ha in area and these form approximately 1.0% of the total surface area of Scotland. Com parable figures for England and Wales are 1700 lakes and 0.05% of the land surface, and in terms of volume. Loch Ness contains more water than all the lakes and reservoirs in England and Wales put together (Smith & Lyle...