Hi there,
Can you explain me why some of you advise for multi spool reel for river fishing ? I never see the use for it (in my type of fishing).
To me only a floating line is enough and I use some furled leader in different density if I want to fish below the water.

No idea, i only use floaters as well. I dont even bother with the furled leaders.

If you are talking about trout fishing then i too only use a light reel with a floating line. Its all i have ever needed.

For salmon fishing its different, i carry different line densities for different water heights.

For river trout I've only ever used a floater. For salmon/sea-trout things may be different but I don't fish for migratory fish so...

I only speak about trout/grayling fishing...