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Hi Sardar, I have not seen any good free hydrogeology courses. That is the reason why I am making my videos. One resource you should look at is the groundwater project: gw-project.org where you can find many free books for download. All the best, Andreas

You are welcome! All the best, Andreas

Groundwater exploration is great fun. Glad you enjoy it! All the best, Andreas

You're welcome Surafel! All the best, Andreas

You are welcome Algassimou! All the best, Andreas

Hi Don, yes it is possible to use it with pumping well data & you use the borehole radius as "r". However, you should ignore any storativity values calculated in this way. For that you need observation well data. All the best, Andreas

Hi Sana, welcome to the channel! All the best, Andreas

@with_ny8178 thanks for your kind words! All the best, Andreas

Thanks for your kind words! Yes, the old fashioned tools never go out of fashion, and often better and more reliable especially in remote areas. All the best, Andreas

You are welcome Hakmatyar! all the best, Andreas

@syedahmedshah4402 you are welcome! all the best, Andreas

You are welcome! All the best Andreas

Yes, Darcy's Law applies to all groundwater flow. All the best, Andreas

Hi Berham, yes it works but you need to leave the file in its original XLS format. Do not save it in XLSX or XLSM format. All the best, Andreas

@@GeosearchInternational Thank you so much

​@GeosearchInternational I have another question, please, Mr. Andreas... Do you have any research topics regarding applications of 2D ERT for my master thesis? I appreciate your help... Thanks.

Hi Berham, ERT is quite expensive and time consuming, so usually it is used if you need to get detailed information over a small area. I have used it to map faults & landfills... other applications include archeological sites, graveyards, and areas which will be excavated such as the entrance to tunnels. I would advise that you meet with your local municipality or local companies, and see if any of them have some needs for a detailed imaging of the sub surface. You never know - maybe they can sponsor you as well. Wish you all the best, Andreas

​@GeosearchInternational The insights you provided are very useful... thanks again.

Hi Swanu, you could try to extract data using a point location, but remember that MODIS uses a 500x500 metre pixel sizes, so you will get an average number for ET/PET over that pixel... and it will only give you data if that pixel has some vegetation. All the best, Andreas

You are welcome! @nataliiabudeniuk2193 All the best, Andreas

Hi Swayam, storativity is unitless: m3/m2/m... Maybe better explained in the Storativity video. Of course we can use it to calculate how much water will be released by an aquifer based on the area and drop in hydraulic head. All the best, Andreas

Hi Swayam, by definition groundwater will be at atmospheric pressure at the water table. Below the water table the pressure will increase by about 1 bar/1 atmosphere every 10 metres of depth due to the weight of the water. All the best, Andreas

@@GeosearchInternational thank you sir !!

Welcome!

Hi Attaur Rahman, My knowledge is mostly via more experienced geophysicists and several years of field geophysical surveys for groundwater exploration. I always found the books to be very theoretical but not so useful for field surveys. I think there are already some books on geophysics in the Groundwater Project, but not sure if it's about conventional geophysical surveys. Have a look at: gw-project.org/books/?_books_categories_facet_filter=investigation-techniques I'm planning a new video on field techniques for resistivity surveys... but am very busy. All the best, Andreas

@@GeosearchInternational many thanks. Please do share some stuff on bore well logging as well.

In the link I sent you I saw a book on geophysical borehole logging. There is also a book by the IAH which can be downloaded free: iah.org/wp-content/uploads/2013/03/IAHbook_ICH9.zip

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

Have a look at the first video I made on this channel: ua-cam.com/video/O7K00PQaQIw/v-deo.html All the best, Andreas

@Eng.Shihabalbalushi, I have been using ESRI ArcView/ArcGIS since 1999, but nowadays I use exclusively QGIS because it is all I need... so my GIS videos are only for QGIS. Regarding ET data I'm using MODIS ET/PET with 500m resolution. Normally I get the time series since 01/01/2000 - see: ua-cam.com/video/cUAtYyGI9mI/v-deo.html. I'm also going to start using FAO WaPOR, since they expanded the dataset to Asia. What exactly do you need to do? Make a map of ET? All the best, Andreas

You're welcome! All the best, Andreas

Thanks Nawaz! All the best, Andreas

Hi Ibrahim, the presentation is PowerPoint and the Excel tool uses VBA to calculate the Theis curve. All the best, Andreas

You are welcome abhishek! All the best, Andreas

I would pick the season when the climate is the best, because it is difficult to work in the heat. During the monsoon your work will be interrupted by rain/thunder, so I guess the post-monsoon would be the best time. There is also the issue of the soil. If it is already wet, the current can enter more easily. However that can be mitigated by pouring water on the electrodes. All the best, Andreas

You are welcome Ayrem! All the best, Andreas

In all my videos you can have a look in the description, where I often share files. For this video there is a Link to pdf notes: bit.ly/3e86loF all the best, Andreas

Hi Tom, sorry I cannot advise you as I don't know the method or the equation which you are using. In any case you need to be very careful with the main input parameters T, K, i, effective porosity, presence of other wells, boundary conditions etc. All the best, Andreas

Thank you for your reply. I solved the equation analytically. It turned out that dupuit-thiem for confined is also for phreatic aquifer if the drawdown is beding corrected by Jacob 1963 equation since it uses the piezometric height relatively to the distance R and und constant pumping well discharge. It follows the law from Darcy. The analytical integral relstes therefore only for the radius. All the rest ist a constant value. The radius is replaced by x and y cartesian system using the Pythagoras and the rule for the rectangular triangle relationship of the intercept theorem.replacing the r the formula can be used for x and y as distance to the well. The integral of derived function leads to the traveltime formula along the center line to the well. tau=-x-ln(1-x) using this formula along the axis includes the downstream speed of the ambiant groundflow as a superposition with the velocity induced by the well pumping rate. This formula gives the information at which point the particle along the y achses and about the traveltime. With this the d50 line can be calculated. Its valid for confined aquifer. But also in phreatic aquifer as long as jacob 1963 drawdown correction is applied. I finished the program with matlab and i wrote the analytical induction that the approach is legitimate. If Ur interested id send you the script and the solution. This is probably the analytical and numerical core of modflow except that modflow uses more information input. But still the derivation of the above formula is the heart piece of any hydrological approach for the traveltime

Hi Tom, you should double check your output with a numerical model just to be sure. It’s so easy to make programming errors. Here is a good overview of different methods for capture zone delineation: www.envirolink.govt.nz/assets/Envirolink/R6-2-Capture-Zone-Delineation-Technical-Report.pdf all the best, Andreas

That is brilliant thank you big time. This is exactly what I was looking for.

You are welcome! All the best, Andreas

Thanks so much! All the best, Andreas

Thanks so much! All the best,Andreas

You are welcome Robert! All the best, Andreas

Hi Akash, thanks so much for your kind words & good luck with your field trip! All the best, Andreas

Thanks for your kind words @chesko7753! You are right - power query is very good at extracting data from various sources, but it is also quite complicated to use when the input table is in a wrong format, so it is not the topic of this video. Only a properly formatted excel table will load correctly in QGIS and that is the message I’m trying to get across. Many people I meet are still trying to load CSV files into QGIS when there is a better way, and I hope that they go for this methodology. All the best, Andreas

Hi Assia, sorry I do not understand your question. can you elaborate? All the best, Andreas

@@GeosearchInternational What about a partially penetrating well? The same steps?

Hi Assia, if your observation well is close to the pumping well you will need to correct the observed drawdown data for partial penetration effects. However, I would always do the first interpretation without any corrections & then compare later. You can find more details on partial penetration corrections here: www2.alterra.wur.nl/Internet/webdocs/ilri-publicaties/publicaties/Pub47/Pub47-h10.pdf All the best, Andreas

@@GeosearchInternational Thank you for your efforts and quick answers

@@AssiaTafrount-vw4jq you are welcome! All the best, Andreas

Hi Mark, are you referring to the India Water Resources Information System? indiawris.gov.in/wris/#/DataDownload You can try to get the data when it is night time in India. Good luck & all the best, Andreas

@@GeosearchInternational Hello thanks for the quick response. Yes the data from the India Water Resources Information System. I'm finding the website very slow to work with. I'll try again at a different time.

Hi Mark, yes, it has not easy. If you want a time series of the water levels, you need to download the data by State and year separately. After that, there is no unique identifier for the wells so you need to create one. I concatenated State-District-Station to make one. There is also a way to access the data using python script, but I have not tried it. All the best, Andreas

Hi Atiqullah, Kajaki is the most important dam in the Helmand River Basin & also there are some interesting studies already completed by the USGS. I wanted to see if they can be replicated using open source data. For example, see my video on the evaporation losses of Kajaki dam. All the best, Andreas

I think the results for your volume is 5100 MCM which is a large number compared to the actual reservoir capacity 1700 MCM.

Hi Habib, the maximum capacity @ 2 metres above the spillway is around 1485 MCM. That is an SRTM elevation of 1020m, or an arbitrary project elevation of 1035.5m. When we make the Elevation-Area-Capacity curves we will always include elevations which are way above the maximum fill level. In this case I have gone up to 1050m SRTM, which would give a volume of 5063MCM. Of course this is just theoretical. The reason for extending the curves is in case some politician decides that it would be a good idea to increase the dam height by "x" metres. I think there were some plans to do this for the Kajaki. If the curves are ready, it is very fast to see the impact of this in terms of flooded land area, and increased evaporation losses from the larger surface area of the reservoir. All the best, Andreas

Never mind! Solved! It was an error with the filepath! Great video, thank you!

Hi Brette, glad it worked! All the best, Andreas

You are welcome Thomas, all the best, Andreas

Thanks Monim! All the best, Andreas

You are welcome Dan! All the best, Andreas

Hi Anwar, Saline groundwater has a higher conductivity - ie lower resistivity than fresh groundwater. A higher clay content has the same effect, so you need to be careful with the interpretation and it is always good to have calibration wells. I have used resistivity surveys to map the fresh - saline interface in coastal aquifers. The change in resistivity is really clear. Usually the currents don’t penetrate much into/below saline groundwater so it may affect the depth of investigation. All the best, Andreas

Thank you for sharing your invaluable experience, Andreas.

@@anwarmaqsood9764 you are welcome! All the best, Andreas

The link should be in the description below the video. All the best, Andreas

Hi Inga, yes SAGA has disappeared but there is a way to link to it. Please see links below. The video is for QGIS windows, but I also included instructions for Mac in the manual. All the best, Andreas ► Link to Manual (PDF): bit.ly/Install_SAGA_in_QGIS_WIndows ► Link to video: ua-cam.com/video/ceBOzPtQvms/v-deo.html

Hi Mazen, All files links are in the description below the video. Have you downloaded the template? Link to the Excel template & data files: bit.ly/3C1himE Link to updated template for 2000-2022: bit.ly/MOD16A2GF_template_zip All the best, Andreas

Hi Fred, the links to files are always in the description below the video: QGIS shape files & Reservoir DEM: bit.ly/3Lc70Ws EXCEL data & calculations: bit.ly/3unSTaz It opens in Google Drive so just click on the download arrow top right. All the best, Andreas

You are welcome Xogen, All the best, Andreas

Hi Phii, there are so many different types of data so it depends what you are looking for. In QGIS there are also many plugins which allow you to download rasters directly. e.g., SRTM Downloader. all the best, Andreas

Hi @assoaljomaily1589 there is no method to detect groundwater directly, except perhaps with magnetic resonance. The magnetic method is looking for changes in the earth's magnetic field so you can use it it you are looking for e.g., igneous dykes if you want to site wells just upstream of them. By electrical method you are probably thinking of resistivity which is the best way to map aquifers. You can use resistivity profiling, resistivity imaging, VES and also electromagnetic methods like TDEM. You can find several videos on resistivity & groundwater exploration in my Hydrogeology 101 playlist. All the best, Andreas

@@GeosearchInternational thank you Mr Andreas ..I have many friends who want to dig wells, but the nature of the layers is gypsum and karst layers, and it is difficult to find water everywhere, and when we dig more than one well, we do not find water except by luck. So one of my friends suggested that he buy a device to detect groundwater from a depth of 10 - 70 meters...that's why I asked you...knowing that I major in geophysics

@@assoaljomaily1589 If you are only interested in shallow wells (<70m) you could try resistivity traversing followed by VES. Karstic areas of limestone will have a lower resistivity so maybe you can map them. As for gypsum, do you have any low quality water in that formation? All the best, Andreas

@@GeosearchInternational array (VES)@@GeosearchInternationalarray @@GeosearchInternational high condictivity@@GeosearchInternational

Thanks so much for your kind words @hydromanor! Glad you found it useful. All the best, Andreas