The connection of hair with nature is not only in its assimilation with water. The Egyptian funerary texts show hair Snw of Isis and Nephtys as an image of both banks of the Nile. According to Pausanias the tears dropping from the eyes of Isis were like the water in the riverbed, so the two mops of hair at both sides of the face could be considered as the vegetation on each bank of the Nile.
For reinforcing this idea we have the Egyptian language, which designates the vegetation as “the hair of the earth” and considers a land with no plants as a “bald land”; therefore the hair is clearly in Egyptian belief identified with the vegetation. The two mourners’ pieces of hair/vegetation would be a metaphoric image of the two banks of the river.
From the natural point of view, we would be here facing a second seasonal step of the Egyptian calendar. The hair sm3 is a symbolic image of the inundation, that happens in the first season of akhet, while the hair Snw is referring to the plants, so the second season of peret. The growing of the plants is a natural rebirth, so making the nwn gesture and throwing the hair assimilated to the vegetation could be understood as a way of transferring the living force to the corpse; in the funerary dimension this would be a way of contributing to the mummy’s resurrection.