The rivers of Eden are symbolic (see: Eden), and carry many levels of meaning.
"And a river went out of Eden to water the garden; and from thence it was parted, and became into four heads. The name of the first is Pison: that is it which compasseth the whole land of Havilah, where there is gold; And the gold of that land is good: there is bdellium and the onyx stone." The land of Havilah is our own physical body, and the gold of this land is the solar atoms from our seminal system, that is to say, the semen’s potable gold. And the name of the second river is Gihon: the same is it that compasseth the whole land of Ethiopia. This second river is the cerebrospinal fluid, which is the other pole of our seminal system. With it we encompass the whole land of Ethiopia, that is to say, the whole of our head and throat, since we form the brain and throat with the cerebrospinal fluid. "And the name of the third river is Hiddekel: that is it which goeth toward the east of Assyria. And the fourth river is Euphrates." (Genesis 2:10-14) The river which goes toward the east of Assyria and the river Euphrates are the two poles of the woman’s seminal system. Therefore, the woman is towards the east of us, because she is the door of Paradise and this door is always towards the east. Eden is sex itself. Thus, the Tree of Life is within Eden itself. The great hierophant Eliphas Levi said that the great magical Arcanum is the Tree of Life and that “at the foot of this Tree is the source of the four mysterious rivers of Eden.” Yet, he fearfully says in a moment of consternation: “Here I must pause, and I fear that already I have said too much.” This is the formidable, unutterable secret which no Initiate has ever dared to reveal. This is the formidable secret of the “Great Arcanum.” The four rivers of Eden are the sexual forces of man and woman. The Tree of Life is in the midst of these four rivers of Eden." - Samael Aun Weor, The Revolution of Beelzebub
"The first river corresponds to the element earth of the Wise (the Tattwa Prittwi). The second river corresponds to the element water (Tattwa Apas). The third river corresponds to the element air (Tattwa Vayu). The fourth river is the element fire (Tattwa Tejas)." - Samael Aun Weor, The Aquarian Message
"In Genesis, written by Moses, the four rivers of Eden are mentioned, the four rivers of milk. These four are the flaming fire, the pure water of life, the impetuous air, and the perfumed elemental earth of the sages (the four tattvas)." - Samael Aun Weor, The Perfect Matrimony