Aquifers for Dummies

 

confined and unconfined aquifers

We don't know how many times we've said it (over two thousand at this point), but when you have a question it's a good bet that you should ask someone who knows the answer instead of someone who doesn't. Put another way, very, very, very few communications majors and English Lit students are qualified to write introductory string theory texts; or, for that matter, books on building Shaker-style furniture. You want a physicist for one and a woodworker for the other. Yet, the website formerly known as eHow.com was built on allowing said communications and English Lit students to pretend to know anything and everything. Hint? they didn't. A case in point is contributor Peter De Conceicao attempting to explain the "Differences Between a Confined Aquifer & an Unconfined Aquifer" for Sciencing.com.

The answer is pretty simple: a confined aquifer is overlain by an impermeable layer, which creates a pressure differential between the aquifer and the atmosphere. There is no overlying impermeable layer in the case of an unconfined aquifer, so the fluids are at atmospheric pressure.

De Conceicao, unfortunately, did not understand the distinction. Heck, Peter didn't even seem to understand the meaning of "aquifer," blithely informing his readers that,

"Aquifers are bodies of water located underground. They may be enclosed within surrounding rock, which is called a confined aquifer, or exist within a layer of water-saturated gravel or sand, which is called an unconfined aquifer."

De Conceicao's first sentence reads as though he thought that aquifers are underground lakes (he may have actually believed that, who knows?). That's because an aquifer isn't a body of water, it is a rock or soil layer that contains water. His daffynitions of confined and unconfined were equally clueless, in particular the "enclosed within surrounding rock" bit.

Pete blundered on in ignorance, further muddying the water by pretending that,

"Aquifers are created when water seeps through earth and permeable rock until reaching a layer of impermeable rock. Groundwater then saturates the surrounding rock or sand, forming an aquifer."

Nope, that's wrong: it's not like water from a dripping pipe spreading out on the basement floor, there's water percolating everywhere.  He also misinformed his readers that,

"Unconfined aquifers are typically below major water courses such as rivers."

We guess he got that from looking at the pictures in his references, but it's just more bushwa. Finally, De Conceicao continued to misinterpret his sources and further confused the issue with such pronouncements as,

"In the case of confined aquifers, replenishment [sic] can take a long time, as its sources of water are underground systems that have to travel long distances."

First, Pete, the word you wanted is "recharge." Second, WTF are those "underground systems" of which you spoke? And third did you not realize that, at least in groundwater, all confined aquifers are unconfined at some point, the area known as the the recharge zone?

This self-appointed expert never used the words "pressure" and "recharge," both of which are essential to the differentiation of confined and unconfined aquifers. That's pretty much all you should expect; however, from someone who had bragged about being a "social commentator" for the late, unlamented Examiner.com. Oh, and Pete? You're the Dumbass of the Day. You're welcome.

SI - HYDROLOGY