Electrical Resistivity Survey: Results & Evaluation - Recommendations Sought - Chitradurga, Karnataka
Submitted by iwp on April 21, 2009 - 22:33
I have undertaken an Electrical resistivity survey method for finding borewell points in my farm plot in Hiriyur Taluk, Chitrudurga District, Karnataka. My farm is located 15km before Hiriyur. I would like to know from the experts about the success rate (or dependability) of this method.
As per the report from Geologist the Land is completely covered over by hard and massive rock. One Bore point recommended in the depth of 300ft at gaps 220ft - 280ft - yielding 1 - 1 1/4inch of water. I wanted to get one more confirmation on this report.
In the neighboring lands (2 plots) 400mts away and other one is 450 mts away has 2 inches of water. Is there any other test which can give more accurate results. Please share your experience and advice.
The Land can be seen from the url:http://wikimapia.org/#lat=13.8558827&lon=76.719085&z=16&l=0&m=a&v=2&search=javan agondana%20halli
In the name of <Javanagondana halli land> highlighted box.
Jagadish Babu
9880495195
Comments
1.
Dear Jagadish Babu,
The resistivity survey is the one of scientific tool/method for giving recommendation of drilling a borewell.
Really, the recommendation depends on resistivity value, curve pattern Geology of area and person, intrepretation capability, these all contributes for recommendation.
Thanks and regards,
C.Vijayakumar
Hydrogeologist
Madras Cements Ltd.
Chennai
2.
Dear Jagadish,
The best way to select sites for well construction with good reliability is to use the electrical resistivity data in conjunction with ground water prospects maps prepared by the National Remote Sensing Agency (NRSA) for most parts of India including Karnataka with funds provided by the Rajiv Gandhi National Drinking Water Mission.
These maps were prepared in 2002 on a scale of 1:50,000 by using IRS-1C/1D LISS-III Precision corrected False Colour Composites (FCC), superimposition of digitised lithological, geomorphological, structural, hydrological & base details and collection of hydrogeological information such as depth to water table, yield, recharge conditions, nature of aquifer materials, types of wells suitable, depth range of wells, yield range of wells, success rate of wells, water quality and status of groundwater exploitation.
As these maps were meant for use by government departments engaged in selection of sites for drinking water wells in rural areas, they are not made available for others. But, when I contacted some of my students working as government geologists engaged in the development of groundwater in rural areas, even they expressed ignorance as to the existence of such maps. The presentation at http://ddws.gov.in/popups/NRSA_files/slide0139.htm that gave details of the methodology followed in the preparation of these maps some time ago is unable open up now.
To view the presentation click here
click here
Under the existing circumstances, one way you can receive further advice in the selection of a well site in your land is to further edit the Wikipedia map you gave by giving the boundaries of your land, stream courses if any, location of sites (points) where your geologist surveyed along with those recommended and not recommended, location of successful and failure wells in the neighborhood, well yields, and how high or low the areas around your land are with reference to your land.
Good luck.
Dr. R. Jagadiswara Rao
Retired Professor of Geology
Sri Venkateswara University
Tirupati, AP 517502
(Presently on a visit to USA)
rjagadiswara@gmail.com
Dr. R. Jagadishwara Rao Professor of Geology Retired Sri Venkateswara University Tirupati, AP 517502, India rjagadiswara@gmail.com
3.
Dear Jagadish Babu,
Using Resistivity as a tool and properly collecting and interpreting the dat one can get a fairly good idea of the subsurface variations.
Problem is the interpretation the same data can be interpreted differently by different people.
There are a vast majority of people who use the resistivity meter but do not really know about the limitations of the equipment in the field leave aside the interpretation of the field data.
If you say that the water yielding zones have been inferred at 220ft and 280 ft, this is probably based on the data that was collected from the borewells in the area. I say this becasue if the zone is that deep it has to be atleast 10 meters thick to be identified. Aquifers of smaller thickness at that depth would probably be missed out during the survey.
It would have been ideal if you could have attached the field data sheet or the interpreted curve that is generated by plotting the field data.
All the same however good the geologist may be there is always a 20 to 25% risk of the interpretation being wrong. it can go both ways, by this I mean that you could get much more or much less water as compared to what has been inferred.
One thing I would like to surely comment upon- there is no such thing as a point where one need to drill to tap groundwater, as groundwater is flowing there will always be atleast 2 points which usually form the alignment of path of flow of ground water.
If there was only one point it needs to be in some corner, or where does the water come from and where does it flow to.
From the link that you have included, you seem to be located in the intra basinal area or Inter basin divide, the water is flowing in different directions away from your property.
But when one looks at the regional picture you seem to be placed over some regional lineament like feature.
As for other tests that can give better results- sorry to disappoint you, but there does not seem to be anything that is so easily available and cheap in India, and anyway all results are based on some assumptions and presumptions, best result can only be obtained by actual drilling.
Best of Luck
Dr. Anil Lalwani
http://www.wellwaterworks.com
4.
T.S.BADRINARAYANAN, GEOSCIENTIST, B SQUARE GEO TECH SERVICES,
tsbadri56@gmail.com
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