×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

What's the difference between transmissivity and K?

What's the difference between transmissivity and K?

What's the difference between transmissivity and K?

(OP)

Let me start out with a personal statement.  I have prided myself in having been able to get through the subject of geology knowing little to none about the field of hydrology.  Now that I am breaking out my old books, I am finding out why.  I believe it is an intrinsically confused subject, with redundant terms and misplaced concepts galore.  Nonetheless, it is a science I now need to know.  

I am curious about the practical aspect of transmissivity.  I noticed that the units used, GPD/ft are very close to hydraulic conductivity, GPD/ft*ft.  Am I right in assuming that transmissivity is just the horizontal component of hydraulic conductivity, for water moving through an aquifer?


Thanks.    

RE: What's the difference between transmissivity and K?

Hi Dirt -

You had to say "practical aspect", didn't you...

Horizontal hydraulic conductivity is essentially the coefficient of permeability of a medium, and it quantifies the capacity of the medium to transmit water.  Units are that of speed (length/time).  The higher the number, the more permeable the medium is.  With some caveats, it's essentially the rate of flow of water through a cross-section of one square foot of the aquifer medium, under a unit hydrualic gradient.

Transmissivity may seem less a nebulous concept if you remember the following relationship, keeping units constant:
T=kb
where T= transmissivity
      k= horizontal hydraulic conductivity
      b= thickness of the aquifer

An example is helpful...
An aquifer with a horizontal hydraulic conductivity of 10 feet/day that has a saturated thickness of 25 feet would have a transmissivity of 250 feet^2/day.
or...
Same aquifer would have a transmissivity of 1870 gpd/ft.

"Gallons per day per foot" is also a typical unit for transmissivity.  To convert between these two units of transmissivity, just remember a cubic foot contains 7.481 gallons, and divide or multiply by 7.481 as the case may be.

RE: What's the difference between transmissivity and K?

(OP)
Thank you.  These concepts seem less nebulous to me.  I am eternally grateful for competent persons like yourself in the world.  I was going about nuts!

I have to admit, those units continue to be cloud-worthy to me.  It seems much easier to consider movement in terms of length/time than [volume/time]/length.  

Thank you again!  Mental clarity is at a premium these days...

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources