Hydrogeology 101: Thiem equation
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- Опубликовано: 29 июн 2020
- This video is about the Thiem equation which describes steady state flow to wells in confined aquifers. We explain the origin of the Thiem equation and illustrate it with a practical example of a hypothetical well pumping from the Lower Neogene aquifer of Kabul, Afghanistan.
For this we use some data from the JICA 2011 report on 'The Study on Groundwater Resources Potential in Kabul Basin in the Islamic Republic of Afghanistan'. You can access the report here: openjicareport.jica.go.jp/pdf...
Link to the Thiem spreadsheet: bit.ly/2JJQJwV
Link to the Neogene confined aquifer example: bit.ly/394uFWm
thanks Mr Andreas. i appreciate what you are doing for us
My pleasure Samir! All the best, Andreas
I watched a few more of your videos today and I just had to comment once again! Many thanks, very clear and concise explanations and you make it easy even for someone like me who easily gets lost in equations and calculations 😃
Glad it was helpful! After a while even the longer equations will become your friends. The trick is to know which equation is the right one to use for a particular project, and also - and this is even more important - what assumptions and conditions apply to each equation. Good luck with your studies & all the best, Andreas
Amazing work. Thanks for the video
Glad you liked it! All the best, Andreas
Hi Andreas. Maybe you can provide some insight. How would you calculate Q in the main pumping well if you want to limit drawdown in a well 100m away to 40m? Many thanks
Hi Rupesh, Actually you need to specify the head, not the drawdown if you use the Thiem equation. Also, this is a steady state equation, so you need to decide what will be the maximum extent of the cone of depression. This is where the amount of recharge from precipitation/leakage equals pump discharge. Let's guess it is 1,000m.
1. Delete all data in the green boxes.
2. Take the pumping test ‘Oude Korendijk’ (after Wit 1963) data..
3. T = 370.45 m2/d, r =100m, r2=1000m, h1=0m, h2=40m.
4. Check the calculated boxes in grey: Head difference or drawdown = 40m which is what you are after. Calculated Q = 28,900m3/day
That's quite a lot. If you use a h2 of 5000m, Q drops to 19,300m3/d.
Hope that helps. All the best, Andreas
Your videos are very helpful. Highly appreciated
You are welcome Thabo! All the best, Andreas
@@GeosearchInternational On the excel worksheet, I can't see the graph for the cone of depression. Do you know how to create it manually so I can use my own parameters?
Hi @@adogjbone4972, In Thiem SS Confined V3 you can enter your parameters and the values will be displayed in the diagram above. There is no separate calculations of the cone of depression for this tool. All the best, Andreas
@@adogjbone4972 In 'Thiem - SS Confined V3.xlsx' you just fill in your data in the green cells and the results should appear in the diagram at the top of the page. This tool does not create any drawdown curve - it just calculates the parameters in the beige cells using the Thiem equation. All the best, Andreas
@@GeosearchInternational Ok thanks Andreas for your hard work. If I'm to use the diagram at the top of the page, how am I to reference it as acknowledgement of your work?
Thank you very much sir. Please a complete field aquifer pumping test procedure video..
Hi Asif, Many videos are on the list - including this one! All the best, Andreas
it was really helpful for me thanks a lot
You are welcome!
Please can it be applied to unconfined unsteady-state conditions? Thank you
Hi Ramon, No the Thiem equation only applies to steady state confined conditions. It can be used for unconfined steady state conditions if we correct the drawdown. For unsteady state conditions you need to use other methods like the Cooper-Jacob straight-line method which you can fit to the late data. Be careful to ignore the delayed yield part of the curve. See ruclips.net/video/4pU336P_TX4/видео.html
Alternatively you can use the Neuman method, but I don't have a video for that yet. All the best, Andreas
Just wondering why a big drawdown means more influence on the surrounding and higher energy costs? and how how do you get the transmissivity was low by the big drawdown?
Hi Huang, A low transmissivity means that there is a lot of resistance to groundwater flow through the aquifer. It means that there are a lot of friction losses in the aquifer, which have to be overcome through a steep hydraulic gradient. The steep hydraulic gradient is only possible if you have a big drawdown in the pumping well. The large drawdown results in higher pumping costs, as you need more energy to lift the water against the force of gravity. Large drawdowns also have a big influence on the aquifer in the vicinity of the pumping well, as water levels in nearby wells will be lowered. I hope that answers your questions. Remember, big drawdown = low transmissivity & shallow drawdown = high transmissivity. All the best, Andreas
@@GeosearchInternational Thank you! I guess when I think over Darcy's equation (Q=KiA) and how much energy takes to mobilize sluggish groundwater, it makes more sense to me.
Hi Huang, if you can visualise equations: T=Kb so Q=Tiw. If the width (w) does not change we can only adjust the Transmissivity (T) or the gradient (i) to maintain the same discharge (Q). Another way to think of it: If you drink coffee - finer ground coffee beans have a lower permeability than coarser ground ones, so you need more pressure to get the hot water to flow through the filter. I have made some videos on an Excel groundwater flow model which I use to visualise pumping wells. See Groundwater flow around wells - Excel model: ruclips.net/video/PvUWXQCEjpc/видео.html and Steady state in pumping wells: ruclips.net/video/9Wmkugy3XdQ/видео.html All the best, Andreas
thank you!
You're welcome Adrienne! All the best, Andreas
so informative, could u share the excel sheet... many thanks
Hi! Here are the latest ones:
Link to the Thiem spreadsheet: bit.ly/2JJQJwV
Link to the Neogene confined aquifer example: bit.ly/394uFWm
All the best, Andreas
@@GeosearchInternational Thanks a lot Mr. Andreas, your efforts are appreciated....
You are welcome! Andreas
very good video sir,
Glad you liked it Surya! All the best, Andreas
@@GeosearchInternational thank you so much for your Guidance, i too made my own video, correct or point out the mistakes if you have time, thank you dear sir, ruclips.net/video/GK3meDrC6K8/видео.html
Hi Surya, Sorry I don't have much spare time so have just briefly looked at your video. Good to see that you are making so much effort to teach your students! My advice is that you track the RUclips statistics see which parts of your video people are enjoying to watch, and which parts they skip. RUclips is a different world from the classroom, and people have more control over what they want to learn. Not easy to keep them all happy. Anyway, good luck and keep up the good work! All the best, Andreas
@@GeosearchInternational thank you so much sir, really thank you, so happy to hear your reply!
❤
Welcome Qadr! All the best, Andreas
so helpful!
Glad you think so Neon! All the best, Andreas
Very helpful!!....thnx......but how did you do that with excel....my mind blew😅😅
Glad you found it useful! Excel is one of the most powerful tools available, and for calculations and plotting of data it is my favourite. All the best, Andreas
@@GeosearchInternational thnq sir..... yesterday is my exam of 'groundwater, wells and pumps' and it was very helpful.🙂
@@Himzz26 That's great! All the best, Andreas