The Pishon River (2:11-12) has been variously identified by scholars with the Nile, the Indus, the Ganges, or other rivers. The lack of any general agreement stems from the fact that no known river matches Moses’ description: "it flows around the whole land of Havilah, where there is gold. The gold of that land is good; the bdellium and onyx stone are there."
"Havilah" itself is of uncertain location, but is generally associated with the western or southern regions of the Arabian peninsula. "Bdellium" is usually understood to be a fragrant resin, found in abundance in Arabia, as are various types of precious and semiprecious stones (the identification of the "onyx stone" is uncertain). The only known Arabian source for "good gold" is the so-called "Cradle of Gold," (Mahd edh-Dhahab), located about 125 miles south of Medina, in the Hijaz Mountains, which currently produces more than five tons of gold a year.
The problem is that there is no river flowing today from this area toward the confluence of the Tigris and Euphrates. But once it was different. A scientist from Boston University, Farouk El-Baz, taking clues from alluvial deposits in Kuwait, carefully examined satellite photos of the Arabian peninsula. There he spotted the unmistakable signs of a river channel cutting across the desert. Originating in the Hijaz Mountains near Medina and the Cradle of Gold, the ancient waterway, currently concealed beneath sand dunes, runs northeast to Kuwait. Dubbed the Kuwait River by its modern discoverer, it once joined the Tigris and Euphrates at the head of the Persian Gulf. Then because of climate changes, it dried up, the archaeologists say, sometime between 3500-2000 B. C.
http://focusmagazine.org/Articles/pishonriver.htm