Wow, that’s so cool. I have never heard this…neat…
Pittsburgh’s Mythical “Fourth River” at Point State Park
For many years, people have talked about Pittsburgh’s mythical “fourth river” flowing underneath the Allegheny and Ohio rivers that acts as the main water supply for the fountain at Point State Park in Pittsburgh. It even has a name-the "Wisconsinan Glacial Flow-and is said to flow from Lake Erie and pass directly under the ‘Point’ before it turns northwest along the Ohio River.
The concept of an ‘underground river’ brings to mind a large cavernous subterranean flowing stream, similar to surface rivers. Such underground streams do exist, but they are generally short and limited to caves and other cavities. Unfortunately, such conditions do not exist at the Point.
Point State Park actually sits on top of 40 to 60 feet of unconsolidated (not formed into rock) sand, gravel, and cobbles deposited 16,000 to 20,000 years ago during the Ice Age. Continental Glaciers advanced into northwestern Pennsylvania with the last ice advance (the Wisconsinan), stopping about 30 miles north of Pittsburgh. As the glaciers retreated, large volumes of meltwater flowed down the Allegheny and Ohio rivers, scouring and eroding out their present river valleys. As the water flow volume subsided, it deposited large amounts of sand, gravel, and cobbles called glacial outwash. What remains of the glacial outwash deposits can be found on the sides of the river valleys, the bottoms of the Allegheny and upper Ohio rivers, and underneath Point State Park.
The glacial outwash is very porous and permeable, making it an extremely good aquifer. Water from the rivers infiltrates this aquifer through a thin layer of clay and silt on the bottom of the present rivers. A 54-foot-deep water-supply well drilled for the fountain on the Monongahela side of the park is in this unconsolidated material. Test pumping the well yielded over 700 gallons per minute and was termed an ‘inexhaustible water supply.’
Journalistic attempts by the media over the years to explain this prolific aquifer in lay terms often used “underground river” in quotes. As the story was retold, the quotes were eventually lost and other embellishments added eventually giving some false authenticity to the concept of an underground river, called the “Wisconsinan Glacial Flow.”
If the “Wisconsinan Glacial Flow” had originated in Lake Erie, which has an average elevation of 570 feet, it would have to rise some 140 feet to the normal river level of 710 feet at Point State Park. Even a mythical underground river doesn’t flow uphill.