You need to travel light when sketching with watercolors on locations. Small A6, A5, and A4 heavy watercolor paper sketching blocks, a few brushes and a sandwich will do! Heavyweight paper doesn’t need stretching as it absorbs more water before it cockles.
Sketching on location will be more vital and immediate than if you paint only in your studio. Gestural movement is what gives life to landscape painting.
Lights transient nature can only be captured with speed and gestural strokes so only use large brushes.
Painting on location with all the paraphernalia of easel, chair and supported palette is all an unnecessary and stereotypical burden.
Take a wad of expendable palette pads, they make it easy to change your palette quickly and so you can respond to changing light conditions.
There is no need to take too many paints with you. A painting is an organised palette and the colors you use will determine the atmosphere of the finished sketch. Organisation is better than chaos, right! The fewer colours you use the more your colour mixing will improve.
Often artists take photographs on location and then work on them once back home. If you like this method, I would suggest that you not only take photographs but also make abundant sketches.
Thwarting the natural tendency to copy what you see will always produce the best results. If you document your experience too well by over playing detailed observations, you reduce the outcomes freshness.
One method could be to take only black and white photographs and sketch in color in parallel. If you choose to paint later at home, you can then combine the two references into something new and exciting.
Art making is not copying what you see but letting the viewer see what you want them to see!