Hydrogeology 101: Groundwater exploration strategy 

You are welcome & good luck with your ongoing groundwater exploration project in Kabul. All the best, Andreas

Bonjour Diaby, thanks for your kind words and wish you success with your master! All the best, Andreas

Thank you for your kind words Mostafa! All the best, Andreas

You are welcome Naqibullah! All the best, Andreas

Thanks Rushil, I’m happy you like it! All the best, Andreas

Glad you liked it! All the best, Andreas

Thank you Thomas! All the best, Andreas

Thank you 🙂 All the best, Andreas

Most welcome Abdirisaq! All the best, Andreas

Hi Ishara, excellent question! Topic 1: Boundaries - All that we can get out of a constant rate pumping test is (i) the aquifer Transmissivity and if it is an observation well then also the aquifer Storativity and (ii) information on how the cone of depression has interacted with nearby flow boundaries (recharge boundary = constant head boundary & barrier boundary = no flow boundary). The presence of flow boundaries you should be able to see in the field. For example next to a big river you would expect a recharge boundary and if you are in an alluvial aquifer next to a mountain you could expect a barrier boundary. Topic 2: recharge zones of a well/wellfield. To calculate the capture zone of a well we need to know the exact elevation of the water table, as well as aquifer parameters. So you need to measure existing static water levels in wells in the area & survey them in so you can get the altitude of the water table. Then we need to draw the groundwater elevation contour lines & a flow net. When we draw the flow net we need to decide if there are any boundaries and what kind of boundaries they are based on topography/surface water features/geology/hydrogeology. Big topic. Once we know the groundwater flow direction near the well we can calculate its capture zone based on aquifer transmissivity and the pumping rate. At this stage it is also important to look at the water balance. Is there enough groundwater recharge to sustain the well & any other users of the aquifer? I will make some videos about this when I have more time. All the best, Andreas

Thanks Shradha! All the best, Andreas

You are welcome! All the best, Andreas

@@GeosearchInternational Sir, I am studying MSc in Hydrogeology in Hungary, what are your advices as an expert in this field. best regards, Osama

Hi Osama, I'm not so sure what your question is, but my main advice regarding a Hydrogeology MSc is that you need to think of it as the first step of your future as a hydrogeologist. Do not think that the MSc certificate is all you need to succeed. It is only the beginning. You need to keep learning throughout your career, and most importantly - read as much as you can and discuss things with other experts in the field. Good luck & all the best, Andreas

Hi Nick, The surveys in Oman and Ghana were with an ABEM Terrameter. The 3D image is from a TDEM survey in Pakistan. Have you seen: Introduction to Resistivity Surveys? ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-MvOR4xY1Mb8.html All the best, Andreas

Hi Dharamveer, glad you liked it. All the best, Andreas

Hi Hajara, sorry I don't have a manual for this. This video is from a presentation I made for my colleagues in Afghanistan. All the best, Andreas

Hi Anna, glad you find my videos useful for your work! I did a lot of groundwater exploration in the Middle East but not as much in Africa as I would like. As a consultant I need to follow the projects - first come first served... All the best, Andreas

Thank you! All the best, Andreas

You're welcome! All the best, Andreas

The reason why I made this video is that I have not seen a clear groundwater exploration strategy described anywhere, so I decided to show the one I have developed over the years. Maybe you can find alternative approaches via Google search, but this is the one that works for me. All the best, Andreas

Welcome Asadullah! All the best, Andreas

Hi Mukhtar, Nice to hear from you. To be a good hydrogeologist means that you need to understand the whole water cycle, and how the water moves both above and below the ground surface. A geophysical survey is just a tool that will give you an insight into the subsurface, so you waste less money drilling in the wrong locations. I have done lots of geophysical surveys in Africa & Middle East and I was lucky to learn from really good geophysicists. So any hydrogeologist can also do geophysical surveys, but then you also need to master the strengths and weaknesses of the equipment and learn all the tricks of the trade. Unfortunately many "geophysicists" are not professional and actually don't know what they are doing. e.g., I have seen so many noisy resistivity curves because people don't plot the data in the field... and then later they try to smooth out the noise. Geophysics is just one tool. If you are looking for groundwater in fractures, you need to understand the tectonic stress field of your project area. Which faults are likely to be open and full of groundwater and which are closed? Then you need to know where the groundwater is being recharged and where it is flowing. There is not much point finding a nice well which is not sustainable in the long run. Also you will need to master hydrochemistry. What is the water quality and what is influencing it? Is there arsenic or fluoride in the water? What are the saturation indexes of the various minerals? Is there likely to be precipitation or corrosion in the well? How does this affect choice of pumps and pipelines? Many questions, but you need to always ask the right ones in order to find the correct answer. That's why hydrogeology is a fascinating subject for me, and even after 30 years I am still learning every day. Wish you best success & all the best, Andreas

@@GeosearchInternational thank you very much Andreas. Your response resonates with what I was looking for which is getting advices from a successfull hydrogeologist. I am still learning groundwater hydrology and chemistry and I am using your advices as well your RU-vid channel videos to better master hydrogeology. I hope to be a successfull hydrogeology who also can do geophysics to help my country and people. I hope I will get the opportunity to learn more from experienced hydrogeologists in the fieldwork. Thanks, Mukhtar

Hi Mukhtar, I like your enthusiasm. If you continue to direct your energy in the right direction there is nothing you cannot achieve. There is so much information available on the internet, so keep reading technical reports & watch those videos! Also, don't forget to talk with the drillers. Often they know more about an area than anyone else. All the best, Andreas

If you have a private plot, you still should do the assessment in the same way. Sometimes you can even do some geophysics outside the boundaries of the plot to get a better understanding. Once you have your conceptual understanding you can decide if there is any potential inside the plot or not. All the best, Andreas

Excellent, 🙏🏻❤️

Thanks! All the best, Andreas

Sorry I have never seen a good one. That is why I’m making these videos to share my experiences. Also, many certificates are just a piece of paper so be careful what you pay for... All the best, Andreas

@@GeosearchInternational thanks for reply brother ☺

Welcome! All the best, Andreas

Hi Hassan, It really depends on the hydrogeology of the area in which you are doing the groundwater exploration, and how much money/time you have available. In most places I would do resistivity surveys, either using VES/profiling or indirectly with Electromagnetic techniques (eg TDEM in dry, non-urban areas). As for the equipment choice - that depends on what is available in your country. I would not advise bringing in equipment which cannot be repaired in your region. All the best, Andreas

@@GeosearchInternational Thank you

Welcome! All the best, Andreas

Hi Rahul, I think the answer is zero for resistivity surveys as we cannot actually detect the groundwater. We are just producing a simplified geo-electrical model of the sub-surface which is depicted as some layers of different resistivities and thicknesses. Which of these layers is an aquifer will depend on the interpretation, which should be based on existing borehole data and calibration soundings next to existing boreholes. If you do a VES, the exploration depth is approximately 1/3 of the AB spacing of the sounding. So for example if your AB is 1200m, then you can expect to see down to 400m. As mentioned before, all this will do is to produce a geo-electrical model. You cannot be sure about the aquifer or how productive it will be until you drill. What VES helps us with is the selection of the best drill sites - for example where the aquifer is the thickest/has the lowest resistivity etc. All the best, Andreas

Hi Oubirah, My professor used to say - first work in hydrogeology for 10 years, then you can play with modelling. So that is the first step - first understand hydrogeology as the RIRO (rubbish in = rubbish out) principle is very important in modelling. You need to develop a really good conceptual model first, then organise all your data and see if the theoretical model matches reality. Usually it is a lot of work, so before you start you need to ask yourself: do you really need it? Often most questions can be answered using much more simple approaches. All the best, Andreas

@@GeosearchInternational thank you so much sire I appreciate your advices 😊

Most welcome! All the best, Andreas

Thanks Ramon! I used to work in Ghana doing small towns water supply in Accra & Eastern regions. If you want to look for groundwater, it is best to have studied geology & hydrogeology as it is a huge amount of information you need to know to be successful. As for jobs, it depends on what is driving the economy. Private sector, donors, NGOs? Best you talk with some of your Ghanaian colleges to see what the current situation is in your country. People will always need water, but the market can be competitive if there are too many "experts" offering their services. Good luck & all the best, Andreas

Thank you.

welcome

Dear Micro, Water which is salty can conduct electricity more easily. That means that is has a lower resistivity which is something which we measure in resistivity surveys. However, clay rich sediments also have low resistivities so you cannot tell from a resistivity survey if the low resistivity areas are due to clay or saline water or even both. That is why your conceptual hydrogeology understanding of the project area is incredibly important. Resistivity surveys are just one of many tools you can use to better understand the groundwater conditions. All the best, Andreas

More videos coming soon! All the best, Andreas

Please to make one video on electrical resistivity & electro magnetic survey for ground water exploration. And it's differences.

Hi MALLIKARJUNASWAMY, Have you seen these videos: Resistivity surveys: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-MvOR4xY1Mb8.html GeoVES software: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-EN0-Fhan3fs.html I have not yet made any videos on EM surveys. All the best, Andreas

Dear Sinky, That is a big topic... I'm planning a new video on resistivity surveys at the moment. All the best, Andreas

Geosearch International hellow Mr Andreas sorry ineed to know which kind of 2D machine is best in geophysical survey ?

Hi Anwary, Sorry I don't recommend any particular manufacturer. However, I recommend that you only do business with companies who have a representative in your country so that they can easily fix things when they break and can also help you with any issues when you first start using the equipment. All the best, Andreas

You need to find out the reason why it has become saline. Is it due to (i) saline intrusion or (ii) saline upconing? If there is saline intrusion in your area, it means that saline groundwater has moved in and replaced the fresh groundwater due to over-pumping of all wells. You will see this if all wells in the area have recorded increased salinity. In that case there is not much you can do & a collective solution is needed - for example closing down wells/lower groundwater abstraction/managed aquifer recharge. If it is due to saline upconing, it means that saline groundwater present below the well is being drawn upwards due to an excessive cone of depression in your well. The solution is simply to reduce your pumping rate. It could of course be a combination of these two effects, so the best thing is to reduce the pumping rate & monitor the electrical conductivity to see if it improves. In any case you should look at alternative water sources - maybe rainwater harvesting from the roof of your house? Good luck & all the best, Andreas

@@GeosearchInternational thanks for information,yes salinity increased everywhere in my area so it means saline intrusion so we can't undo it but what if we dig shallow wells atleast we will get fresh water for one or half season for farming is that possible ? and which time is better for survey to find freshwater just after monsoon when water level is high or end of summer when water level is low ?

Is the well near the coast, or where is the salinity coming from? How many aquifers are there? Is it just one, or are there several? If you have active recharge during the monsoon, all you need to do is to live in equilibrium with this recharge - only pump what is recharged from rainfall - and the water quality should be fine. If the well is screened throughout its depth what you could do is pull up the pump in stages and pump every 3-6 metres to see if the water quality improves. Alternatively you could run an EC/temperature log of the well & see if there is a change in water quality with depth. Good luck and all the best, Andreas

Thank you Charity 😃 All the best, Andreas