Hydrogeology 101: Groundwater flow around wells - Excel model
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- Опубликовано: 8 июл 2024
- This video is about groundwater flow around wells in a confined aquifer. We will use an Excel model to look at (i) the effect of moving wells closer to recharge boundaries, (ii) what happens when we double the discharge rate of a well, (iii) how wells interact in a wellfield to produce overlapping cones of depressions and (iv) we will also see the effect of recharge basins and recharge wells on the piezometric surface.
This is an educational video & part of the Hydrogeology 101 course.
Credit for the design ideas of the Excel model goes to Carlos Molano, International Association of Hydrogeologists (IAH), Vice President for Latin America and the Caribbean. iah.org/about/council/carlos-...
You are welcome to download a copy of the model via Google Drive: bit.ly/3NdLAJZ
However, you are fully responsible for whatever you decide to do with it - it is an educational spreadsheet only. Please use professional modelling software if you want to design a wellfield, artificial recharge scheme etc...
#RadialFlow #wells #ConfinedAquifers
Very interesting! Maybe the easiest way to expain to students! simply using Spreadsheet! Could you please share the Excel file? Thanks.
Thanks Yajun Li. I have put a link to the model in the description below the video. Let me know what you do with it. All the best, Andreas
Wow...this is the next-level teaching skill. visualization through spreadsheets make very easy to understand the pumping in and out effect on the sub-surface.
Glad it was helpful Ankit! All the best, Andreas
thanks for the effort! Your videos really help me better understand groundwater flow, pumping tests etc. I just finished my bsc in geoscience and hope to find a a job as hydrogeologist.
@Diclofenac_ Thanks for your kind words & congratulations for finishing your BSc. I hope you find an interesting job. Hydrogeology is a massive subject, so keep reading and talk with the older generation... Also after a few years consider an MSc if you want to specialize. All the best, Andreas
Not only fully educational but also so satisfying to Watch , very appreciate your work sir. I wish I could learn how you do the modeling to reach such an amazing and well constructed excel arc, which I never knew can do much more than just plotting graf until I watched your videos
You are welcome Noor! If you want to play with the Excel model, there is a link in the description under the video to download it. All the best, Andreas
Fantastic work on this series of videos on Hydrogeology. Creating the support material for the videos and editing them must have been a lot of work. I am grateful for what you have given us. Fascinating
Glad you like them Lila! Each video takes about a week, mostly for planning & thinking how I'm going to present the ideas. I have already given the lectures, but condensing it all into an interesting video is another story... All the best, Andreas
@@GeosearchInternationalI have been binge watching your videos, so you certainly have succeeded at making them interesting. I am moving to a homestead and you have given me the idea to invest in a used a earth ground tester to identify the aquifers
That sounds exciting! Have a look at my video on Groundwater Exploration Strategy. Geophysical surveys are just a small part of the process of looking for groundwater. Wish you the best, Andreas
Thanks so much for these interesting videos. They are very illustrative.
You're welcome!
Excellent presentation and useful material. Thanks for sharing.
Glad it was helpful Mostafa! All the best, Andreas
Amazing sir 😍😍
Thanks Fuzel! All the best, Andreas
Nice
Thanks
Do you think we should every consider using a constant head boundary as you have shown here in any real world applications? I am thinking that it can lead to very inaccurate results as it is acting as an infinite supply of water.
Thanks for doing tutorials on these kinds of topics. I'd be very happy to share your work wherever I can because I genuinely want these kinds of videos to rise to the top in the YT algorithm, not just those silly tik tok stuff. Although I do enjoy my occasional dose of tiktok
A good question, and I think the key issue is that any model is only as good as our conceptual model of the world. If we stick in a constant head boundary, it will supply an endless amount of water to the model, so we need to look at that in the water balance and ask ourselves if that body of water can really supply so much water without a reduction in head / drying up. If you are pumping next to a big lake or river, maybe a constant head boundary is OK. The key is to look carefully at the water balance.
As for tik tok I don't watch it, but I have always supported the concept of work hard - play hard! All the best, Andreas
Great video. Might you have videos related to, Analytic element modeling of groundwater flow. ( Haitjema, H. M.)
Hi James, Glad you liked the video. Sorry, I have not made any videos so far on groundwater modelling. Maybe later? First I need to do more on the simple tools like flow nets. All the best, Andreas
Hi Andreas, as a geologist I'd like to thank you for sharing this powerful, smart and easy-to-use excel model. A great tool for teaching and showing how water wells work. My first question is about model V2: in the GW Heads sheet, hydraulic conductivity K has m2/d as unit. As far as I know it should be m/d. My second question is about model V1 vs model V2: in V1 you used Transmissivity, in the second hydraulic conductivity: did you change the formulas underpinning the model or are there other reasons? Thank you again so much and all the best, Roberto
Hi Roberto, Thanks so much for finding the copy-paste error in the Unconfined model! So many people have watched the video and you are the first to spot it. I have updated the unit - of course K is in m/d.
There are two different models: 2D-SS-CON GW Model V1.xlsx is for steady state confined conditions, and 2D-SS-UNC GW Model V3.xlsx is for steady state unconfined conditions. The unconfined formulas are more complicated as the aquifer is being dewatered, and there are separate calculations being carried out in a hidden sheet called "V". All the best, Andreas
I was wondering if you have a video explaining further the numerical process of the equation you used to calculate ground water heads.
what if your reservoir didnt have a recharge would you just remove that part of the equation?
what if the aquifer was unconfined and the constant head was not constant, how would that change the equation?
Would you have a video explaining the equation further.
Hi Mahdi, Sorry I don't have any videos about the equations. As I mentioned in the video, this Excel model is based on one made by Carlos Molano, so I don't have all the references for it.
The equation for confined aquifers does not need to be changed. If you remove all the pumping wells and the recharge, you will end up with a flat surface as the heads are controlled by the outer boundary cells which are all set to 100m (you can change this if you like). Once you add pumping wells, recharge wells or general recharge the heads will be recalculated as long as you have iterations enabled in Excel.
For unconfined aquifers you cannot use this model. Please see my video Steady state in pumping wells: ruclips.net/video/9Wmkugy3XdQ/видео.html You can download the unconfined model in the description below the video. All the best, Andreas
Hello,
thank you for the beautiful modeling lesson during the pump test. I wanted to try it on my own example, but after downloading it, excel doesn't work, or if I delete - reset the values in the wells tab, and put other values, the graphic stays with the default values. So if I just put in a well with no observed well, it should only make one cone, but I am left with the default two cones without any change.
How to solve this, do you know?
Hi David, I just downloaded 2D-SS-CON GW Model V1.xlsx and it still works fine. Please check your Excel Options. Under Formulas - Calculation options, you need to have Workbook Calculations set to Automatic. Also enable Iterative Calculations and set them to Maximum Iterations 1000 and Maximum Change 0.00001
When you add a new well in the Wells sheet, it should show up immediately if the number is high enough (eg 10,000 m3/d). Hit F9 to repeat the calculations. Hope that solves the issues. All the best, Andreas
Hello sir after long time with another question.
Step test
With help of step test data, calculate the value of B and C and are used in equation to determine drawdown and diacharge in equation.
s=BQ+CQ2.
Above is the only purpose of step test or anything more.
Hi Kaleem, There are two purposes for step tests:
1) Calculate the well efficiency, V = BQ/(BQ+CQ2), so that we can see if the well has been designed and constructed properly.
2) Decide what discharge rate to use for the long-term pumping test, so that the well is stressed as much as possible without dewatering it.
All the best, Andreas
Thanks a lot.
Welcome Kaleem! All the best, Andreas
Hello sir,
Could you share the excel sheet for step test.
Thank you.
You will have to wait till the video, as it needs to be explained to be useful. All the best, Andreas
When I change stuff in the sheets (e.g. wells) it doesnt refresh the model plots and the data in the GW heads sheet. I tried refreshing and all, nothing seems to be working ;/
Got it to work - had to allow iterative calculation in the excel settings first :)
edit: now the model changes with different well settings/positions, but it creates a "bowl shaped" drawdown even without any wells.
Hi @Diclofenac_ Initially you have the model that I created with 2 wells, so there is a cone of depression in the centre. Then you deleted the wells, so Excel will start to iterate. With each iteration the model will increase the heads in the cone of depression to slowly reach the 100m head around the model. If you have set Excel up for 1000 iterations, you still end up with about 1 or 2 cm drawdown in the centre after 1000 iterations - the bowl shape you mentioned. Just hit the save button a couple of times and after a few more iterations it should approach the 100m of head in all cells. All the best, Andreas
Hi sir, do you have an email?
Hi Jhan, If you have any questions please use this comments section as I am bad at answering emails - get too many every day and I don't have time to read them. All the best, Andreas