Swims that are good in summer will be equally reliable in winter, unless river conditions force the fish to move out.
When higher, faster flows force them to move, they only move as far as they need to in order to find a comfortable station.
This is where the ability to read the flow variations of a winter river is crucial to determining where the fish will relocate.
Examining the set of the various flows of a river at winter level soon confirms that what at first glance may appear unvarying current speed and direction from bank to bank is actually anything but uniform.
There are usually numerous variations in the current, with regular divisions between fast and slower water, some of which are very pronounced.
Such divisions between fast and slower flows are known as creases, and they are among the most reliable of all winter swims for many species.
The Water Surface Whatever the speed of flow, the water surface itself gives us vital clues to the sub-surface contours and vegetation.
Certain areas run smoothly, while others are constantly or intermittently turbulent.
Whether it be a gentle ripple or a substantial boil, such surface disturbance is a reflection of underwater irregularities.
A constant boil or vortex is caused either by the shelving up of the river bed or by a large obstruction, such as an old tree stump.
A shelving river bed is often accompanied by a diversion of flow if the bottom gravel slopes across river, and such a feature is a natural food trap, attractive to all species.
But this is only true where the surface flow is relatively smooth away from the actual feature.
If the current is fierce enough to result in heavily broken, boiling water, fish will vacate the area.
Constantly boiling water, caused by large irregular bottom debris, is rarely worth a second look.
The whirlpools caused by such obstructions make it very uncomfortable for fish to cope with the constantly changing currents.
One exception might be an area of very localized boiling, created where a large boulder or something similar rests on otherwise smooth gravel.
Such a feature often causes a depression on the downstream side hollowed out by the current, and that creates a food trap.
Such swims are most effectively fished upstream.
It is important to differentiate between heavily broken water caused by large debris, and the moderate constant ripple of shallows.
The surface of shallow water will ripple even if the bottom is quite fine gravel containing small stones, and such areas only become unfishable when heavy flood water creates unacceptable levels of turbulence.
Depressions These hollows in the river bed in extensive shallows are excellent holding areas, especially for chub, roach and barbel; look for smooth bits of surface amongst the ripple.
Even a small depression is an important swim to locate, particularly if it is located in a long stretch of shallow water, when it may be the only natural holding spot in that section of river, particularly in high water.
It is quite amazing how many big fish can pack into a tiny depression.