WHAT’S THE POINT?.......PITTSBURGH’S 4TH RIVER???? EarthCache

Did you ever wonder where all the water that flows from the fountain at Point State Park comes from??...... I lived in southwestern Pennsylvania for almost 50 years, and it wasn’t until after I moved away, that I learned more about not the 3 ‘rivers’ of Pittsburgh, but also talk about the possibility of a 4th river.  But, as once speculated, this 'underground water source' is not really a river, although in some ways it certainly has some similarities to one.  Here’s some early history about the geography and geology of the area that will help you understand how this 'underground water source' came to be, and why it is important to Pittsburgh today.

 Many years ago, the waters of the Ohio and Allegheny rivers flowed northward to an ancient Lake Erie Basin. During the ice age, glaciers pushed southward toward our area, and the great river valleys were filled with rock and gravel. The bottom of our 'underground water source' had been formed (carved) mileniums ago by the northward flowing rivers.  The northward flow of the rivers was blocked by glaciers, and new outlets southward were created. Clay and silt were deposited over the layers of gravel, sealing them off from the surface rivers that were formed 'shortly' thereafter.

Pittsburgh's 'underground water source' is what geologists call an 'aquifer', but it differs from other aquifers in that most are irregular and widespread and do not follow a channel. This aquifer also processes more water than most other aquifers. Therefore, the Pittsburgh's sand & gravel aquifer is possibly compared and confused with being an underground river since it has more similar characteristics with a true river than other aquifers.  It is not a river in the same sense that the Allegheny or Ohio are rivers. The size of Pittsburgh’s aquifer varies from one-half to one mile wide and its depth from 15 to 35 feet. It might be compared to an oval tunnel, completely filled with rocks and gravel. The sides and bottom are solid rock and the top is silt and clay. This clay top that separates it (where necessary) from the Allegheny and Ohio varies from several feet to as little as three feet thick in some places. 

The Harmony Society, (although undocumented) may have been the first to tap this hidden resource by drilling a well in the Ambridge area in 1873. Whether they realized the significance of this well is uncertain. But by this time geologists were being hired to locate oil wells on lands in Northern Pennsylvania, and one of these geologists may have reasoned that pure water could be found by tapping the glacial drift of the Allegheny-Ohio Valley. 

By far the most visible evidence of downtown Pittsburgh's aquifer is the impressive Point State Park Fountain. The fountain uses water pumped to the surface by specially designed pumps housed in two small buildings to the left and right of the fountain. By using these pumps, the water can reach a more impressive height and create a showy impression.  Water pumped through the fountain is not entirely from the aquifer. The fountain's water is also comes from the other nearby rivers. So great is the amount of water that flows slowly beneath the Golden Triangle, that many nearby businesses also supplement their water source from this 'underground water source'/aquifer.

Reference:

 Bureau of Topographic and Geologic Survey......links: 

 http://www.dcnr.state.pa.us/cs/groups/public/documents/document/dcnr_006820.pdf (this issue of Pennsylvania Geology has an article that explains how the Three Rivers and the aquifer formed on pages 2-8) http://www.dcnr.state.pa.us/cs/groups/public/documents/document/dcnr_014598.pdf (this short book discusses PA’s groundwater and aquifers; pages 19 to 20 cover Point State Park and the fountain specifically) http://wesa.fm/post/how-pittsburghs-ancient-aquifer-busts-fourth-river-myth (this news article explains in very simple language that the aquifer water is groundwater) http://dcnr.state.pa.us/topogeo/groundwater/gw_education/bad_hydro/index.htm (this article addresses several misconceptions about groundwater in Pennsylvania)

FTF honours go to sharon12!!!!!!!