Hi, my name is Andreas de Jong and on this channel I publish educational videos on hydrogeology, hydrology, GIS & data management. I am a freelance consultant in water resources management & associated capacity building of institutions. I will try to answer your questions in the comment section underneath each video, so please don't send me any emails.
I'm working on many different projects at the moment, so it is difficult. I have many plans for more videos, but each one takes about a week to produce so I am not making many of them nowadays. All the best, Andreas
Thanks for this great video that clears all the concepts regarding ERS. Could you please record a video for IP survey using Dipole-Dipole and Pole Dipole Arrays. It would be very helpful
You are welcome Yasir! Sorry, I have never used IP for groundwater exploration surveys, only for mineral exploration in Ireland, so I am not an expert. All the best, Andreas
Yes, I am asking for mineral exploration. It's okay, but if you have any material regarding the IP, then please share the links with me, which might be helpful for me. Thanks
Sorry I am not up to date with IP. Some links: www.gfinstruments.cz/version_cz/downloads/ARES_Short_guide_Res_IP_Water_survey%202019-01-16.pdf hendragrandis.wordpress.com/wp-content/uploads/2008/03/electrical_surveying_ip.pdf
thank you for your good explanation on resistivity, I am an agronomist and want to drill a well. a technician explored 2 points se1 and se2 in the field, he recommends se1 to me while his master recommends se2, I am hesitant about the choice and the depth, the data is below: Point SE1 : • Résistivity (p) en Ω.m : 40,5 ; 4,93 ; 770 ; 26,1 ; 94,4 ; 346 ; 194 ; 20,8 • Thickness(h) en m : 23 ; 1,65 ; 1,79 ; 32,2 ; 34,5 ; 65,8 ; 35 • Depth (d) en m : 29 ; 30,7 ; 32,5 ; 64,7 ; 99,2 ; 165 ; 200 Point SE2 : • Résistivity (p) en Ω.m : 55,8 ; 4,37 ; 623 ; 224 ; 41 ; 49,1 ; 190 ; 982 • Thickness (h) en m : 30 ; 0,688 ; 1,74 ; 30 ; 39,6 ; 54,9 ; 43,1 • Depth (d) en m : 30 ; 30,7 ; 32,4 ; 62,4 ; 102 ; 157 ; 200 please give us your point of vue. thaks.
I have never considered that one could add a link to a repository in an attribute table, to essentially extend the available data within a data set. That broadened my horizons. Good bye lousy pivot tables!
Sir.thanks for this tutorials it's been of tremendous benefit to me however, I instead of polygons used point stations, unfortunately there was no statistical file in the final download. Can you help me in how I can access this statistics file
The way MODIS algorithm works is that it needs vegetation in a pixel to calculate ET and PET. If you get no data it is probably because your location is barren ground. Even for point locations I would always use a polygon of at least 1 km2 or larger. Also check that there is vegetation in the area. All the best, Andreas
Thank you very much for making this video, you have no idea how much this video helped me, your explanation is very detailed but still on point. Once again thank you
Hello sir is their any complete course offered on Hydrogeologist and any suggest books please sir Your explaination is extraordinary ways I loved it sir keep explain all remaining topics sir please
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
@@GeosearchInternational sir atleast make complete videos how Bore pointing in the field sir Like Schlumberger array method use take reading than after how to make points or location identify and said to farmers air
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
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
@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
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
"storativity is defined the volume of water that an aquifer releases from storage per unit surface area of aquifer per unit decline in the component of hydraulic head normal to that surface." sir this is the definition of storativity. If it is a volumetric term then how come it is unitless without any unit as cubic cm or litres ?
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
sir we know that water is at greater than atmospheric pressure in the confined aquifer. Similarly what will be the pressure of water in an unconfined aquifer ? will it be equal to t or less than 1 ?
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
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
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
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
@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: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-cUAtYyGI9mI.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
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
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
Can I plot superposition of q_0 + q_well in order to find the distance of the 50 day line ragarding traveltime. I did this in an confined aquifer. But I don't know if I can use the same matlab script for unconfined aquifer.
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
