Hydrogeology 101: Storativity
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- Опубліковано 28 лип 2024
- This video is about the storativity (S) of aquifers, also known as the storage coefficient. Storativity is a key parameter which we need for groundwater resources studies. We will look at the key concepts of storativity in unconfined aquifers - specific yield (Sy) & specific retention (Sr), and confined aquifers - specific storage (Ss) & storativity (S). In confined aquifers we will discuss the concepts of aquifer compressibility (total stress, effective stress & pore fluid stress) and water compressibility. We will do an example calculation of storativity for a sandy gravel aquifer using published alpha & beta values.
00:00 Introduction
01:13 Definition of storativity
01:38 Specific yield in an unconfined aquifer
03:25 Storativity in a confined aquifer
05:19 Definition of specific storage
06:19 Definition of storativity
07:07 Typical ranges of storativity in confined aquifers
07:59 Sources of water when confined aquifers are decompressed
08:17 Mechanism 1: Compression of the aquifer
11:54 Definition of compressibility (alpha)
12:26 Mechanism 2: Expansion of water
12:54 Definition of water compressibility (beta)
13:10 Equations for specific storage (Ss) and storativity (S)
15:45 Summary and conclusions
Link to Excel Storativity Calculator: bit.ly/3wkPFlx
This is an educational video & part of the Hydrogeology 101 course.
#Hydrogeology #Storativity #StorageCoefficient
This was the best explanation I have ever seen! Thanks a lot :)
You're welcome Pam! All the best, Andreas
I didn't clearly understood when I heard these definitions in my class, now they are clear, thank you. Great explanation.
You're very welcome SaiPrasad! These concepts are a bit abstract, so difficult to explain, especially for confined aquifers. Glad it makes sense for you! all the best, Andreas
Amazing video. I remember studying Biot's theory and linear poroelasticity in grad school. All of the textbooks and literature I've read always makes storage of porous media seems like such a convoluted concept. This videos makes the distinction between of storage of confined and unconfined units in such a concise and easy to understand language. I wish I had found this video when I was a student.
Thank you so much for your kind words! All the best, Andreas
Simple and effective explanation. Thanks and please keep up with these great short videos.
Thanks, will do! All the best, Andreas
Great lecture! You made the concepts very easy to understand! Thank you
You are welcome Rigzen! All the best, Andreas
Thank you very much sir for this lucid explanation of storativity. I was able to understand the confined aquifer part only because of this video. I am indeed very grateful to you. Thank you once again!!
You are most welcome Diwakar! All the best, Andreas
This + sometimes cross-checking my favorite hydrogeo text book helped me to get a better grasp of how confined aquifers work!
Glad you find it useful! All the best, Andreas
It was wonderful and crystal clear thank you so much you saved a master student from confusion
You're very welcome Essi! All the best, Andreas
Thank you for the explanations😊.... Glad I came to know this channel.. Happy to learn new concepts on hydrogeology:)
Welcome Anusha! All the best, Andreas
Thanks for this excellent explanation. Waiting for more like this....
Welcome! All the best, Andreas
Excellent Explanation , please Make More of these
Thank you, I will
All the best, Andreas
Great explanation . Thank you Andreas
You are welcome Kshitiz! All the best, Andreas
Very well done. Thanks for making such nice videos. Produce more on the pumping test.
Thanks! There are many videos planned. All the best, Andreas
Man, you've been helpful for my hydrogeology class this semester honestly. But I've made the mistake of watching these videos on my main youtube and now i just keep getting your vids recommended to me even when im on break from studying
Guess youtube just doesnt want the learning to stop
Hi Pusa, I'm glad that my videos are useful! The UA-cam algorithm is actually quite good but sometimes you need to help it. If you click on the three vertical buttons next to a video that you are not interested in, you can select "Not Interested" or "Don't recommend this channel". However, I hope that you continue to watch my other videos on QGIS, River Basin water balances or Google Earth. All the best, Andreas
Its okay Mr. Andreas, hopefully I do get to use the other videos for the rest of my undergrad since you're great at explaining them. Might even use them for my thesis one day haha. Thanks again!
You are welcome Pusa! All the best, Andreas
Hello Sir Andreas, I find myself watching these again to refresh myself for finals. Just wanted to say thanks again, sadly my hydrogeology class didn't touch on the topics I thought it would but these videos have been wonderful nonetheless. Wishing you the best.
Hi Pusa, glad it was useful & wish you all the best for the future! Andreas
Thank you for wonderful presentation
You are most welcome Santosh! All the best, Andreas
Very well explained
Simple and understandable
Keep the good work up
Thank you Ashoqullah! All the best, Andreas
thank you very much,, please keep posting videos
You are welcome Ali, All the best, Andreas
very clear explanation. thank you
You are welcome Rahel! All the best, Andreas
Thanks a lot! It was very didactic.
You are most welcome Dayan! All the best, Andreas
There's one thing I still don't get my head around: It's quite obvious to me, that the specific storage of an unconfined aquifer equals (more or less) the "dewaterable" porosity (specific yield). Why that is makes sense, as it is the unit volume of water we get per unit area per unit length of drop (so volume of water per volume of aquifer, basically). But If the Storativity is the unit volume of water per unit volume of aquifer per length of drop of the hydraulic head, that should also yield the "dewaterable" porosity, only as 1/m, - or why not?
And - why in the world is the S = Ss*(aquifer thickness)?
To say it simple - just from the definition given here (or anywhere else) I don't get the (or why there is a) difference between S and Ss
Hi @Diclofenac_ What you need to remember is that a confined aquifer is not dewatered. It is depressurised only.
Specific Storage (Ss) = Volume released from storage per unit volume of aquifer per unit drop in head. i.e., how much water is released from 1m3 of aquifer if the pressure drops by 1m.
Storativity (S) = Volume released from storage per unit surface area of aquifer per unit drop in piezometric head. i.e. how much water is released over the whole aquifer depth (b) if we look at a m2 of aquifer area, and depressurise the aquifer by 1 metre. 𝑺=𝑺𝒔∗𝒃
Once the peizometric surface drops below the top of a confined aquifer, it becomes unconfined and S = Sy. ie the aquifer will start to dewater/drain.
All the best, Andreas
How did you calculate the water released from the exampled confined aquifer?
Hi Huang, The Storativity (S) of an aquifer is the specific storage (Ss) multiplied by the aquifer thickness (b). It is the volume of water released from storage per unit surface area per unit drop in piezometric head. Our unit is the metre (m), so if we take a m2 of aquifer surface, and reduce the head by 1m, the volume of water released over the entire aquifer thickness underneath this m2 will be equal to the storativity (S). In the video I showed the typical range of storativity in a confined aquifer as 5 * 10(-5) to 5 * 10(-3). i.e., 0.00005 to 0.005. This is the volume of water that will be released. The unit is cubic metres of water & there are 1000 L/m3, so it works out as 0.00005 * 1000 = 0.05 Litres at the low end to 0.005 & 1000 = 5 Litres of water at the high end from each m2 of aquifer.
Confined aquifers do not release much water and that is why we end up with large cones of depressions around pumping wells. If we pump too much and the pumping water level in the well drops below the top of the confined aquifer, it will become unconfined we will start to dewater the aquifer at the specific yield. Hope that makes sense. All the best, Andreas
May I know which software u r using for delivering the class
Hi Seshu, I use MS PowerPoint for the presentation with 3D objects, some of which are transparent. The MORPH option for the transitions between some of the slides gives the animation effect. All the best, Andreas
I join others to share my appreciation for your work!
Why do you think profs make that so complicated? Maybe they don't want us to understand the material because they consider us as potential rivals?? :D
You are welcome ZT! Please don't blame the profs. It's really difficult to explain abstract things using simple words. That's why many people make things more complicated than they need to be. Less is more... All the best, Andreas
Sir kindly make a video on piezometric surface
Have a look at the first video I made on this channel: ua-cam.com/video/O7K00PQaQIw/v-deo.html
All the best, Andreas
Grazie 😊
Welcome Habibullah! All the best, Andreas
Thanks
Welcome!
Sir, I am student of geology. Can you suggest some good books that shall help understand hydrogeology clearly. Books that have a bit simple language to decipher 😢
Hi Swayam, have a look at the Groundwater Project. They have just released their 50th free book on groundwater: gw-project.org/books/ All the best, Andreas
Great job you have done & Your excellent explanation is very clear as sunny day .
Could you please share with us if it's available these slides with amazing animation?
Have good day Good lucky ....
Thanks Liban, I'll upload a PDF of the presentation soon with the text. All the best, Andreas
@@GeosearchInternational
Thank you for sharing & updating.
Sorry Liban, I still have not uploaded the document. Soon.. Alll the best, Andreas
Hello, if you dont mind, can you share the spreasheet ? Thankyou in advance
Dear Ezzatul,
Thanks for the reminder! I have uploaded the file & here is the link to Storativity Calculator: bit.ly/3wkPFlx
Let me know if you find any mistakes.
All the best, Andreas
@@GeosearchInternational Thank you. May God Bless you !
You are welcome! I just watched your video on the aquifer model. Well done, you are a natural teacher! All the best, Andreas
@@GeosearchInternational It was for my hydrogeology class assignment. Anyway thankyouu !
Excuse me, Sir. can you explain how to calculate water release volume from storativity. I still don't understand why it has to be multiplied by 1000. Thank you for the answer. It helps me.
Sorry, I just realized that the multiplication of 1000 in the equation is to change volume units. Thank you in advance for the material. I'm still watching your video list on Hydrogeology 101.
Hi Rizky Agung, most mistakes in hydrogeology calculations are because of problems with conversion between units so I'm glad you are asking the right questions! All the best, Andreas
How can i thank you sir . I am really blessed. Thank yiu so much. Sir could you please tell me how can i make these aquifer images ? . Paint or some software? Please respond sir i will be waiting for your reply sir
You are most welcome Asif. All my presentations are done in MS PowerPoint. I make the objects in 3D and make them look realistic using real pictures of sand & transparency effects for the water. The animation is achieved using Transitions-Morph. It is quite advanced use of PowerPoint, so not so easy to learn unless you have time and determination. Good luck & all the best, Andreas
@@GeosearchInternational thank you very much sir. Can we make such images in Coreldraw
I'm sure you can, but I don't use that software. All the best, Andreas
Thanku Sir 🙏
You are welcome Anand! Happy New Year & All the best, Andreas
@@GeosearchInternational Happy New Year Sir 🙏