my message kept bouncing back (problem with Yahoo?) I'm sending a new
attempt to answer your question.

-----Message d'origine-----
De: Gutierrez Alexis
Date: vendredi 29 octobre 2004 18:18
À: 'hydrologymodel@...'
Objet: RE: [hydrologymodel] Thank you Mr. Gutierrez Alexis

Yes Gouraw, the interpretation method is different according to the geology.
You have methods for porous media, others for fissured aquifer, others for
double porosity media. Methods also vary according to the type of aquifer
(confined or unconfined; semi-confined with a leaky aquifer...) and
corrections can be made according to the type of well (partially penetrtaing
well; pumping well with head loss; skin effect and so on). Finally, boundary
effects (barrier or recharge) may affect significantly your interpretation.

In order to remain pragmatic I would suggest you to start with the simplest
method : the Theis formula, (or even the Jacob approximation if your pumping
time is big enough) and check wether you get a good fit or not with
realistic parameters. Even a fissured unconfined aquifer can be interpreted
with Theis when your radius of influence is wide so that the fissure network
can be assimilated to an homogeneous equivallent porous media and the
depletion of the water level is moderate compared to the thickness of the
aquifer.

This should give you a rough estimate of your transmissivity, which is in
many cases, sufficient.

If you need more accuracy you can use specific softwares. You will find on
the net many softwares proposing many different methods. You don't need Pest
as they have their own fitting engine. AQTESOLV for instance proposes
methods with well storage effect. However, as soon as a software proposes
its own adjustement, it's becoming very difficult to know what's you're
doing and you end up playing a video game. So be carefull, especially if you
lack experience in this domain, not to use complex methods with many
parameters which will end in a perfect fit but with irrealistic results.
In my company (French geological survey)we use ISAPE, a software which is no
more commercialised, but whose philosophy is to let the user propose
realistic values and where you can add or remove well effects or boundary
influence. I wish this approach were more widespread.

Sincerly yours;
Alexis Gutierrez
BRGM / EAU
3 Av. Claude Guillemin
BP 6009
45060 Orléans Cedex 2
FRANCE


-----Message d'origine-----
De: gouraw undale [mailto:g_undale@...]
Date: vendredi 29 octobre 2004 07:08
À: Gutierrez Alexis; 'hydrologymodel@...'
Objet: [hydrologymodel] Thank you Mr. Gutierrez Alexis



Mr. Gutierrez Alexis,

First of all I would like to thank you for the information you sent.
It will be helpfull for me while conducting the pump test.

Another thing I would like to know is, the method to be used for
determination of aquifer parameters differs with the geology/lithology
of the area i.e different layers and characteristics of the soil layers.

The aquifer is the unconfined aquifer, with the saturated thickness of
around 30m made up of lateritic soil which is highly permiable.

Anddo you know any software which can determine the aquifer parameters in
large dia. wells taking in to account the well storage effect.
Can I use the PEST model for this.

So, if you have any information regarding this please send it to me.

Thank you.
Gouraw



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