Great video. You explained the concepts much better than my professor could. Can you also share the excel template you used for Dupuit's example, similar to the one you shared for Thiem's equation?
Thank you, sir, I am currently struggling to understand my professor on groundwater hydraulics and your videos really helps me understand his lecture more. kind regards from the UK. I am currently doing my Masters in Hydrogeology with not much background on Mechanics. Your videos motivate me to learn more.
You are most welcome Maria! I also did my MSc Hydrogeology in the UK at UCL many years ago & I was privileged to have a great teacher - Glyn Jones. He told me once that what is most important is not to be able to derive equations, but to know when to use them and what their limitations are. I think that is the secret to becoming a good hydrogeologist. You need to learn how to visualise groundwater flow - especially understand the water balance - and then know which tools to use. For visualisation we have so many new tools nowadays, not just complex modelling software. I'm especially interested in Excel because it is widely available - check out my other videos. In 2013 I started teaching hydrogeology in Afghanistan, and it is the most difficult job I have ever done. Much harder than being a consultant to EU/WB/ADB... some people can visualise things using equations (maybe your prof?), but many - like myself - need to see it in 3D. It all depends on how your mind works, and that is another fascinating topic! I wish you all the best with your studies & if you have any questions about my videos I will try to answer them. All the best, Andreas
@@GeosearchInternational Yes, my professor does explain hydraulics by deriving equations as he use to be a mathematician. I am also a visual learner like yourself so I particularly like seeing hydrogeology in 3D. p.s. I am doing mine at the University of Birmingham. Thank you Andreas, I will let you know if I have any questions.
Hi Maria, Good luck with your course & be patient. It takes many years to become good in hydrogeology & actually you never stop learning. All the best, Andreas
Hello Sir , I really appreciate that share your knowledge and experience with us moreover you have worked in my country in unsecure situations. would you mind if you specified the well point location(X,Y)? or can you mention the district name please?
Hi Rohullah, this example is based on typical aquifer parameters in the Logar wellfield of Kabul. It illustrates the dangers of urbanisation on groundwater recharge. As soon as irrigation is cut off by urban areas, many water wells will no longer be sustainable because recharge no longer balances discharge. This results in rapid groundwater drawdown as we can see in many parts of Kabul. You could of course try MAR, but that would mean keeping all the old irrigation canals open inside the city, and flooding them whenever the Rivers are full of water. Unfortunately this option was never explored before as the old irrigation canals are mostly filled with solid waste and even have buildings inside/ontop of them. Another issue is that the canals would need to be desilted annually after each flood, which of course needs O&M funds. However, surely this is would be cheaper than bringing in water from far away, especially downstream of Kabul where there are high pumping heads to overcome. All the best, Andreas
Thanks Erazem, this formula applies only to steady state conditions so you can use it to estimate the amount of water you need to pump at steady state out of a well, a quarry or a pit, but you should not use it for pumping test analysis. For that I recommend that you start with the Cooper-Jacob straight line method. See ua-cam.com/video/4pU336P_TX4/v-deo.html All the best, Andreas
Thanks for this! I can't understand most of the technical details, but I'm grateful for a lot of the perspective you provided. One segment of intrigue I have now is I'm wondering what you meant by "young water"? I had been under the impression that all water was created at the same time. I'd love if you could shed some light on this. Thanks!
You're very welcome! The water we drink today is the same water the dinosaurs drank so it is not really young as the water cycle is a continuous process that has been going on for millions of years. For hydrogeologists "young groundwater" just means that it has been recharged not so long ago. e.g., if we find tritium (3H) in the groundwater, it must have been recharged from precipitation contaminated by the atomic explosions in the 1950s/early 1960s. Have a look at: pubs.usgs.gov/fs/FS-134-99/ All the best, Andreas
@@GeosearchInternational Just one question regarding unconfined aquifers. In this method of Dupuit-Forchhmeier, staedy state condition needs to be achieved and that is costly and time consuming from environment point of view. I know that is why people go for the Theis method as it is quite similarly behaves at start of pumping and also solves under unsteady state. But what is alternative way (method) to tackle unconfined aquifer than Dupuit-F test?
The easiest way to deal with unconfined aquifers is to use the Cooper-Jakob straight line method on the late part of the data. Initially the drawdown is fast and follows the Theis curve. Then it slows down due to delayed yield, and once that has caught up with the declining water table we are back onto a Theis curve. Normally for unconfined aquifers you can use the Neuman method, but usually Cooper-Jakob is just as good especially if you only have a pumping well so specific yield/storativity cannot be calculated.. see ua-cam.com/video/4pU336P_TX4/v-deo.html all the best, Andreas
Hi @travelwonder, the Cooper and Jacob (1946) solution may be used for the interpretation of pumping tests in unconfined aquifers if Jacob's correction is applied to the drawdown data measured during a test (Kruseman and de Ridder 1994). See: www.aqtesolv.com/cooper-jacob-unconfined.htm However, if the drawdown is small compared to the aquifer thickness, then it does not matter and you can use the uncorrected data. For any pumping test in an unconfined aquifer I would always use the straight-line method first on the uncorrected data to get a first estimation of Transmissivity in pumping wells, and T & S if you have observations well data. Later you can do the Jacob correction to the data if you know the aquifer thickness, and try out more complicated methods such as the Neuman solution. All the best, Andreas
Thank you sir! But I have some puzzles ramain to be solved. I noticed that in a video the "Dupuit-Forchheimer equation" in your video was referred to as "thiem equation for unconfined aquifer" (ua-cam.com/video/7ZvnsA-aVMA/v-deo.html) whereas in another video the Dupuit-Forchheimer equation was used to describe the yield-water level relation for plane strain condition (ua-cam.com/video/IlUEOMYyGcE/v-deo.html) Unluckly, I cant find the source of Forchheimer, P. (1886). "Über die Ergiebigkeit von Brunnen-Anlagen und Sickerschlitzen". Z. Architekt. Ing.-Ver. Hannover. 32: 539-563. Could you please give me a more convincing explanation or an available source?
Hi 孙彦晓, the Dupuit-Forchheimer equation describes steady state groundwater levels for a pumping well in an unconfined aquifer. It can also be used to describe groundwater flow between two canals as shown in Martin's video. Note that the aquifer thickness (b) is equal to the hydraulic head and reduces as we approach the pumping well but that the hydraulic conductivity (K) does not change. This equation is also known as the Dupuit or the Dupuit-Thiem equation. Basically, the Dupuit-Forchheimer equation is the same as the Thiem equation with corrected drawdown (s’) instead of actual drawdown. I don't know how good your German is, so best if you have a look at Kruseman & de Ridder, (2000), Analysis and Evaluation of Pumping Test Data; ILRI publication 47. It is available for free online. All the best, Andreas
@@GeosearchInternational Sir, thank you for your elaborated explanations. However, there are still some points I want to discuss with you. (1) I have found the related descriptions In Kruseman & de Ridder Analysis and Evaluation of Pumping Test Data; ILRI publication 47. For example, in section 5.2.1 "Thiem-dupuit's method", eq.(5.7) is the Dupuit-Forchheimer equation in your video, and is claimed to be "aslo known as the formula of Dupuit" in the literature. However, in my previous understanding, Dupuit equation can only describe the yield-drawdown relation of the pumping well (without observation wells), which means there are no h2 and h1 of the observation wells in Dupuit equation, only H (water level in the recharge boundary) and h0(water level in the pumping well), according to Dupuit 1863. Études Théoriques et Pratiques sur le Mouvement des Eaux dans les Canaux Decouverts et à Travers les Terrains Perméables. So, is there any possibility that the related description in Kruseman & de Ridder is not accurate enough? (2) In contrast, the Thiem and Dupuit-Forchheimer equations are used to describe the yield-drawdown relation when one or more observation wells exist. Although their forms can be the same if the drawdown in the Dupuit-Forchheimer equation were replaced by the corrected drawdowns, in my opinion their are still not the same thing, since the meanings of the parameters have been changed. I get the knowledge from your videos that Thiem equation is applicable to the confined aquifer, and there is a T(h2-h1) in the numerator, whereas the Dupuit-Forchheimer equation is applicable to the unconfined aquifer with a difference of square between h2 and h1 in the numerator. However, before I watched your video, some of the literatures in my language (Chinses) tell me that the "Dupuit-Forchheimer equation" in your video (using actual drawdown instead of corrected drawdown) is called "Thiem equation for unconfined aquifer". Then, I coincidentally watched your videos which tell me the equation turns out to be the "Dupuit-Forchheimer equation". Therefore I am confused. Now I am writing a thesis concerning dewatering, and I want to accurately cite the references about these equations. Can you tell me where the "Dupuit-Forchheimer equation" in your video was firstly reported? I wonder if it is first reported in "Forchheimer, P. (1886). "Über die Ergiebigkeit von Brunnen-Anlagen und Sickerschlitzen". Z. Architekt. Ing.-Ver. Hannover. 32: 539-563.", or in Günter Thiem' PhD thesis (1906) Hydrologische Methoden. But I am not available to these two literatures and I cant read German neither. Can you help me to confirm it? Maybe it is not critical, whereas the most important thing is knowing how to utilize these equations. However, I still want to get the imformation. Looking forward to your reply and being enlightened by you again. Best wishes
Hi 孙彦晓 , I have not done any historical analysis of the name of this equation, and in the end it does not matter. If I was working in China, I would refer to it as whatever name the technical people there are used to seeing, or you will confuse them in the same way as my video has confused you. People call this equation by different names because it was discovered by different people independently - Dupuit, Forchheimer and you can even add Thiem if you correct the drawdowns for unconfined conditions. I was educated in the UK, and there I was taught to use different symbols (eg for Transmissivity) from what is used in my native country, The Netherlands. So it is important to always show your equation and beneath it what all the symbols mean and in what units they are in. Hope that helps & all the best, Andreas
@@GeosearchInternational You used commas as decimal and thousand separators, found it a bit confusing (with the 1km value). Didn't want to be overly critical as the channel is truly excellent.
Hi Nikola, you raise a very important point which is the confusion about commas and points. In most of the English-speaking world points are used for the decimal separators and commas for the thousands. This is what I have been using in the videos, though it may be better to go for a space between the thousands. So instead of r0 = 1,071m it should be 1 071m. The problem is that unless you use a hard space, it can split the number over two lines. I actually started my first two years of school using the non-anglophone system (commas instead of points for the decimal separator). Will try to stop the confusion in future videos. Thanks again & all the best, Andreas
Great video. You explained the concepts much better than my professor could. Can you also share the excel template you used for Dupuit's example, similar to the one you shared for Thiem's equation?
Thanks for the reminder! Here is the link to Excel template on Google Drive: bit.ly/3utgp28
@@GeosearchInternational Thank you so much!
welcome! all the best, Andreas
Andreas, thank you very much for great explanation and visualisation! Practical cases and Excel program are also great!
Hi @Oleg Li, Glad you found them useful! All the best, Andreas
Thank you, sir, I am currently struggling to understand my professor on groundwater hydraulics and your videos really helps me understand his lecture more. kind regards from the UK. I am currently doing my Masters in Hydrogeology with not much background on Mechanics. Your videos motivate me to learn more.
You are most welcome Maria! I also did my MSc Hydrogeology in the UK at UCL many years ago & I was privileged to have a great teacher - Glyn Jones. He told me once that what is most important is not to be able to derive equations, but to know when to use them and what their limitations are. I think that is the secret to becoming a good hydrogeologist. You need to learn how to visualise groundwater flow - especially understand the water balance - and then know which tools to use. For visualisation we have so many new tools nowadays, not just complex modelling software. I'm especially interested in Excel because it is widely available - check out my other videos.
In 2013 I started teaching hydrogeology in Afghanistan, and it is the most difficult job I have ever done. Much harder than being a consultant to EU/WB/ADB... some people can visualise things using equations (maybe your prof?), but many - like myself - need to see it in 3D. It all depends on how your mind works, and that is another fascinating topic!
I wish you all the best with your studies & if you have any questions about my videos I will try to answer them. All the best, Andreas
@@GeosearchInternational Yes, my professor does explain hydraulics by deriving equations as he use to be a mathematician. I am also a visual learner like yourself so I particularly like seeing hydrogeology in 3D. p.s. I am doing mine at the University of Birmingham. Thank you Andreas, I will let you know if I have any questions.
Hi Maria, Good luck with your course & be patient. It takes many years to become good in hydrogeology & actually you never stop learning. All the best, Andreas
Hello Sir ,
I really appreciate that share your knowledge and experience with us moreover you have worked in my country in unsecure situations. would you mind if you specified the well point location(X,Y)? or can you mention the district name please?
Hi Rohullah, this example is based on typical aquifer parameters in the Logar wellfield of Kabul. It illustrates the dangers of urbanisation on groundwater recharge. As soon as irrigation is cut off by urban areas, many water wells will no longer be sustainable because recharge no longer balances discharge. This results in rapid groundwater drawdown as we can see in many parts of Kabul. You could of course try MAR, but that would mean keeping all the old irrigation canals open inside the city, and flooding them whenever the Rivers are full of water. Unfortunately this option was never explored before as the old irrigation canals are mostly filled with solid waste and even have buildings inside/ontop of them. Another issue is that the canals would need to be desilted annually after each flood, which of course needs O&M funds. However, surely this is would be cheaper than bringing in water from far away, especially downstream of Kabul where there are high pumping heads to overcome. All the best, Andreas
Really great video. How, if possible, can this method be applied to single-well pumping test, without drawdown info at distant points? Thanks.
Thanks Erazem, this formula applies only to steady state conditions so you can use it to estimate the amount of water you need to pump at steady state out of a well, a quarry or a pit, but you should not use it for pumping test analysis. For that I recommend that you start with the Cooper-Jacob straight line method. See ua-cam.com/video/4pU336P_TX4/v-deo.html All the best, Andreas
Thanks for this! I can't understand most of the technical details, but I'm grateful for a lot of the perspective you provided. One segment of intrigue I have now is I'm wondering what you meant by "young water"? I had been under the impression that all water was created at the same time. I'd love if you could shed some light on this. Thanks!
You're very welcome! The water we drink today is the same water the dinosaurs drank so it is not really young as the water cycle is a continuous process that has been going on for millions of years. For hydrogeologists "young groundwater" just means that it has been recharged not so long ago. e.g., if we find tritium (3H) in the groundwater, it must have been recharged from precipitation contaminated by the atomic explosions in the 1950s/early 1960s. Have a look at: pubs.usgs.gov/fs/FS-134-99/ All the best, Andreas
@@GeosearchInternational You answered so quickly, thank you! This information is greatly appreciated. (And super interesting!)
Welcome! All the best, Andreas
Your are amazing instrcutor
Thanks for your kind words! All the best, Andreas
@@GeosearchInternational Just one question regarding unconfined aquifers. In this method of Dupuit-Forchhmeier, staedy state condition needs to be achieved and that is costly and time consuming from environment point of view. I know that is why people go for the Theis method as it is quite similarly behaves at start of pumping and also solves under unsteady state. But what is alternative way (method) to tackle unconfined aquifer than Dupuit-F test?
The easiest way to deal with unconfined aquifers is to use the Cooper-Jakob straight line method on the late part of the data. Initially the drawdown is fast and follows the Theis curve. Then it slows down due to delayed yield, and once that has caught up with the declining water table we are back onto a Theis curve. Normally for unconfined aquifers you can use the Neuman method, but usually Cooper-Jakob is just as good especially if you only have a pumping well so specific yield/storativity cannot be calculated.. see ua-cam.com/video/4pU336P_TX4/v-deo.html all the best, Andreas
@@GeosearchInternational Thanks for the hint. But cooperjakob method is not for confined aquifer. I am looking for unconfined aquifer.
Hi @travelwonder, the Cooper and Jacob (1946) solution may be used for the interpretation of pumping tests in unconfined aquifers if Jacob's correction is applied to the drawdown data measured during a test (Kruseman and de Ridder 1994). See: www.aqtesolv.com/cooper-jacob-unconfined.htm
However, if the drawdown is small compared to the aquifer thickness, then it does not matter and you can use the uncorrected data. For any pumping test in an unconfined aquifer I would always use the straight-line method first on the uncorrected data to get a first estimation of Transmissivity in pumping wells, and T & S if you have observations well data. Later you can do the Jacob correction to the data if you know the aquifer thickness, and try out more complicated methods such as the Neuman solution. All the best, Andreas
Thank you sir!
You are welcome!
Thanks, got my homework done
You are welcome Xogen, All the best, Andreas
congratulations u went tru all the vids
Welcome! All the best, Andreas
Thanks
You're welcome!
You're welcome!
Thank you sir! But I have some puzzles ramain to be solved.
I noticed that in a video the "Dupuit-Forchheimer equation" in your video was referred to as "thiem equation for unconfined aquifer" (ua-cam.com/video/7ZvnsA-aVMA/v-deo.html)
whereas in another video the Dupuit-Forchheimer equation was used to describe the yield-water level relation for plane strain condition (ua-cam.com/video/IlUEOMYyGcE/v-deo.html)
Unluckly, I cant find the source of Forchheimer, P. (1886). "Über die Ergiebigkeit von Brunnen-Anlagen und Sickerschlitzen". Z. Architekt. Ing.-Ver. Hannover. 32: 539-563.
Could you please give me a more convincing explanation or an available source?
Hi 孙彦晓, the Dupuit-Forchheimer equation describes steady state groundwater levels for a
pumping well in an unconfined aquifer. It can also be used to describe groundwater flow between two canals as shown in Martin's video. Note that the aquifer thickness (b) is equal to the hydraulic head and reduces as we approach the pumping well but that the hydraulic conductivity (K) does not change. This equation is also known as the Dupuit or the Dupuit-Thiem equation. Basically, the Dupuit-Forchheimer equation is the same as the Thiem equation with corrected drawdown (s’) instead of actual drawdown. I don't know how good your German is, so best if you have a look at Kruseman & de Ridder, (2000), Analysis and Evaluation of Pumping Test Data; ILRI publication 47. It is available for free online. All the best, Andreas
@@GeosearchInternational Sir, thank you for your elaborated explanations. However, there are still some points I want to discuss with you.
(1) I have found the related descriptions In Kruseman & de Ridder Analysis and Evaluation of Pumping Test Data; ILRI publication 47.
For example, in section 5.2.1 "Thiem-dupuit's method", eq.(5.7) is the Dupuit-Forchheimer equation in your video, and is claimed to be "aslo known as the formula of Dupuit" in the literature. However, in my previous understanding, Dupuit equation can only describe the yield-drawdown relation of the pumping well (without observation wells), which means there are no h2 and h1 of the observation wells in Dupuit equation, only H (water level in the recharge boundary) and h0(water level in the pumping well), according to Dupuit 1863. Études Théoriques et Pratiques sur le Mouvement des Eaux dans les Canaux Decouverts et à Travers les Terrains Perméables. So, is there any possibility that the related description in Kruseman & de Ridder is not accurate enough?
(2) In contrast, the Thiem and Dupuit-Forchheimer equations are used to describe the yield-drawdown relation when one or more observation wells exist. Although their forms can be the same if the drawdown in the Dupuit-Forchheimer equation were replaced by the corrected drawdowns, in my opinion their are still not the same thing, since the meanings of the parameters have been changed. I get the knowledge from your videos that Thiem equation is applicable to the confined aquifer, and there is a T(h2-h1) in the numerator, whereas the Dupuit-Forchheimer equation is applicable to the unconfined aquifer with a difference of square between h2 and h1 in the numerator. However, before I watched your video, some of the literatures in my language (Chinses) tell me that the "Dupuit-Forchheimer equation" in your video (using actual drawdown instead of corrected drawdown) is called "Thiem equation for unconfined aquifer". Then, I coincidentally watched your videos which tell me the equation turns out to be the "Dupuit-Forchheimer equation". Therefore I am confused. Now I am writing a thesis concerning dewatering, and I want to accurately cite the references about these equations. Can you tell me where the "Dupuit-Forchheimer equation" in your video was firstly reported? I wonder if it is first reported in "Forchheimer, P. (1886). "Über die Ergiebigkeit von Brunnen-Anlagen und Sickerschlitzen". Z. Architekt. Ing.-Ver. Hannover. 32: 539-563.", or in Günter Thiem' PhD thesis (1906) Hydrologische Methoden. But I am not available to these two literatures and I cant read German neither. Can you help me to confirm it? Maybe it is not critical, whereas the most important thing is knowing how to utilize these equations. However, I still want to get the imformation. Looking forward to your reply and being enlightened by you again. Best wishes
Hi 孙彦晓 , I have not done any historical analysis of the name of this equation, and in the end it does not matter. If I was working in China, I would refer to it as whatever name the technical people there are used to seeing, or you will confuse them in the same way as my video has confused you. People call this equation by different names because it was discovered by different people independently - Dupuit, Forchheimer and you can even add Thiem if you correct the drawdowns for unconfined conditions. I was educated in the UK, and there I was taught to use different symbols (eg for Transmissivity) from what is used in my native country, The Netherlands. So it is important to always show your equation and beneath it what all the symbols mean and in what units they are in. Hope that helps & all the best, Andreas
@@GeosearchInternational Your points make sense, Sir! Thanks a lot. I have learned a lot from you.
@孙彦晓 you are asking the right questions, which is the only way to find the right answer! All the best, Andreas
Those decimal commas and points...
... and your point is?
@@GeosearchInternational You used commas as decimal and thousand separators, found it a bit confusing (with the 1km value). Didn't want to be overly critical as the channel is truly excellent.
Hi Nikola, you raise a very important point which is the confusion about commas and points. In most of the English-speaking world points are used for the decimal separators and commas for the thousands. This is what I have been using in the videos, though it may be better to go for a space between the thousands. So instead of r0 = 1,071m it should be 1 071m. The problem is that unless you use a hard space, it can split the number over two lines. I actually started my first two years of school using the non-anglophone system (commas instead of points for the decimal separator). Will try to stop the confusion in future videos. Thanks again & all the best, Andreas