The River Nith flows east from the hills of South Ayrshire, then south through the towns of New Cumnock, Sanquhar, Thornhill and Dumfries, some 64km to the Solway Firth. Much of the river is of slack water with occasional falls of Grade I, mainly in the lower section. However, for a stretch of about 12km the river runs through the Drumlanrig Gorge and here its fall is more pronounced. In this section alone the fall of the river is about 250m and the river flows over a series of rapids, which can be as difficult at Grade V in high water. For its last few miles, after the town of Dumfries, the river flows into a tidal estuary. The Nith is a relatively short river with a small catchment area and hence it rises and falls fairly dramatically. The river is certainly at its best after heavy rain and it can be in condition at any time of the year. For most of the length the river valley is used by the A76, which is the main Dumfries
- Cumnock trunk road and allows easy access to the river at various locations.