Genesis 2:11-14: "The name of the first is Pishon: 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. And the name of the second river is Gihon: the same is it that compasseth the whole land of Ethiopia [Cush]. And the name of the third is Hiddekel: that is it which goeth toward the east of Assyria. And the fourth river is Euphrates."
Map represents southern Mesopotamia, present-day Iraq, as it existed at the time of the earliest cities before the Flood, at 3500-3000 BC.
The fourth river is easiest to identify as the well-known Euphrates, which today is joined by the other rivers forming the Shatt al-Arab before emptying into the Persian Gulf. At this point in history the gulf region extended further north and all the rivers emptied directly into the Persian Gulf. The Hiddekel is the Tigris, the "great river" Daniel stood beside (Dan. 10:4). It originates in the region of Assyria, flowing southeast until it joins the Euphrates at a point east of Assyria, just as stated in the Bible.
M'Causland identifies the Gihon as the "Gyudes" of the ancients, the modern Karkheh joined by the Kashkan River in the region of Cush, or Kush, in Eastern Mesopotamia. Today it is called Khuzistan, a province in the southwest corner of Iran, formerly home to the Kassi of the cuneiform texts.
Driver places Havilah "most probably" in the northeast of Arabia on the west coast of the Persian Gulf: "The gold of Arabia was famed in antiquity." Hastings identified Havilah as “the ‘sandy’ region of northern Arabia, which extended westward towards the frontier of Egypt.” Archaeologist Juris Zarins identified an ancient river bed in this region from LANDSAT space photos as the likely ancient Pishon.
Farouk El-Baz, a Boston University scientist, studied pebble distributions in Kuwait and was led to the same conclusion, a river once flowed into this country from the Hijaz Mountains in Saudi Arabia. He dubbed it the “Kuwait River.” In an article for Biblical Archaeological Review, James Sauer associates the Kuwait River with the Pishon.
Put in perspective, the most ancient cities of southern Mesopotamia, Eridu and Ur were located near the junction of these rivers, and Eridu when it was first settled on the Persian Gulf was furnished fresh water via canal from the Euphrates.