Running waters in Scotland vary from small trickles and seepages in headwaters to large rivers such as the Tay which has the greatest mean annual flow of all British rivers. There are striking differences between rivers flowing to the north and west and those to the south and east as a result of climatic and topographic differences.
The timing of peak flows consequently varies geographically in response to rainfall patterns and to waterlogging of the soil. In some years, rivers draining from the Cairngorms experience Alpine characteristics with high spring flows due to snowmelt but these patterns are changing.
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