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RE: [gwmodel] Minimum permissible distance between bore holes in hard rock aquifers

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  • asokg@tce.co.in
    Dear SIr, Thanks to Dr. Limaye for his considered opinion. Any study on Hydrology has to be planned on Water Shed basis and any study on Hydrogeology has to
    Message 1 of 10 , Nov 7, 2012
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      Dear SIr,

      Thanks to Dr. Limaye for his considered opinion. Any study on Hydrology
      has to be planned on Water Shed basis and any study on Hydrogeology has
      to be planned on watershed and aquifer boundary basis keeping in view
      confined aquifer, unconfined aquifer and leaky aquifer. However, neither
      farmers nor industrialists nor urban planners are interested in these
      types of regional studies. Most of the EIA reports of major projects do
      not touch the problems related to hydrogeology and ground water
      pollution. Many major mining projects are being planned without any
      systematic regional hydrogeologic studies to assess the damage to be
      inflicted on aquifers which are basic sources of water supply to our
      rural population. Not clear whether the Draft National Water Framework Act
      will suggest any solution to these problems. Anyway this is related to
      National Scenario. At personal level I am interested to know about
      availability of any good book or literature with field examples on Hard
      Rock Aquifer in India./ any other country.



      "Dr. Limaye" <limaye@...>
      Sent by: gwmodel@yahoogroups.com
      11/07/2012 02:11 PM
      Please respond to gwmodel@yahoogroups.com
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      Subject RE: [gwmodel] Minimum permissible distance between bore holes in hard rock aquifers

      Dear Members:

      This is a good discussion on the minimum distance between two bore wells
      in hard fractured rock aquifers. As S is highly variable and T is erratic
      and anisotropic, models may only be made to convince the politicians /
      policy makers but not to the technical people who know the limitations.

      Practical way is to try an approach with watershed basis. From the total
      area of the watershed deduct the area near the edges (which is mostly
      barren and unsuitable for agriculture) and the area under dry-land
      farming. Thus you get an area mostly near the 1st, 2nd and 3rd order
      streams, suitable for irrigational development. The annual recharge from
      rainfall (about 10% of the rainfall) over the watershed would concentrate
      in this area. Let this area be "A hectares". Then make an estimate of the
      annual pumpage from the existing wells and divide by the number of
      existing wells so as to get average annual pumpage per existing well.
      Divide the annual recharge from rainfall by this average annual pumpage
      per existing well, so as to get the maximum number of wells which could be
      supported by the watershed. Let this number be "N wells." Then within the
      watershed there could be " N / A " wells per hectare. "One well per
      hectare" gives a spacing of 100 m. "Four wells per hectare" give a spacing
      of 50 m. (Assuming a square pattern)

      This gives some technical satisfaction and some relation to the average
      field conditions. Models based on specific data points would not represent
      the watershed. In practice, all these N wells would never be dug/drilled
      so that some ground water outflow would still take place from the
      watershed. Plus, if a program of recharge augmentation through soil &
      water conservation activities and forestation is undertaken by the agency
      promoting irrigational development, then it would increase the recharge to
      ground water from rainfall. Furthermore, if the farmers use non-efficient,
      traditional irrigation methods then about 30 % of water applied for
      irrigation would percolate below the root zone and reach the water table
      as "return flow". All these factors assure sustainability.

      At field level, the farmer is the owner of ground water and is free to
      drill anywhere he pleases. The control on spacing or on pumpage is
      possible only through the Gramsabha (Village meetings) and social
      pressure. But not many Gramsabhas are eager to implement this. Government
      legislations are not effective at village level.

      Groundwater management is thus skewed between the technical people who
      have no control at the field level and the farmers who do not like the
      meddling by technical people, except advising them on good locations for
      drilling / digging.

      Dr. Shrikant Daji LIMAYE. B.Engg, M.Tech (Geophysics), PhD (Hydrogeology)
      Director, Ground Water Institute (NGO), Pune, India
      Project Leader, UNESCO-IUGS-IGCP Project GROWNET: website
      www.igcp-grownet.org
      Past President, Association of Geoscientists for International Development
      (AGID),
      Past Vice President (Asia) & Hon. Life Member, International Association
      of Hydrogeologists (IAH),
      Ambassador, International River Foundation, Brisbane, Australia and
      Vice-President, International Association for Promoting Geoethics
      (IAPG),Rome.
      ===============================================================================

      -----Original Message-----
      From: gwmodel@yahoogroups.com [mailto:gwmodel@yahoogroups.com] On Behalf
      Of asokg@...
      Sent: Wednesday, November 07, 2012 12:04 PM
      To: gwmodel@yahoogroups.com
      Subject: RE: [gwmodel] Minimum permissible distance between bore holes in
      hard rock aquifers
      Importance: High

      This is a good reply. Actually Hard Rock Aquifers have to be analysed
      partly as pipe flow (Turbulant) & Partly as Porous Media System . In the
      case of turbulent flow the head loss is proportional to square of velocity

      and in porous media hydrodynamics the head loss is proportional to
      velocity . Thus the overall equation has to be defined through a series of

      subequations. I would like to know whether any reference book or manual
      written in a lucid manner is available to cover these aspects.

      "JPF CONSULTORS" <jpfcon@...>
      Sent by: gwmodel@yahoogroups.com
      11/06/2012 08:21 PM
      To <gwmodel@yahoogroups.com>
      cc
      Subject RE: [gwmodel] Minimum permissible distance between bore holes in
      hard rock aquifers

      Hi, in my opnion is useful to define first the orientation of the main
      fracture systems that define the preferent flow path.

      Considering that wells are taking water of a “pipe system” defined by
      these dominant fracture systems, the point is for ex. if you have one well

      is avoid to locate a new well following the direccions of fractures. That
      means that direccion is more important that distance. If the new well cuts

      the same “pipe” the former well will loss yield.

      Of course because the high ansitropy of the system wells could have strong

      yield differences between them but following that rule you avoid to loss
      yield in existing wells and reduce interferences.

      Jordi Pujadas Ferrer
      JPF CONSULTORS
      C/General Castellvi nº 3
      43400 MONTBLANC
      tel . 977 861 300
      jpfcon@...

      De: gwmodel@yahoogroups.com [mailto:gwmodel@yahoogroups.com] En nombre de
      asokg@...
      Enviado el: martes, 06 de noviembre de 2012 13:11
      Para: gwmodel@yahoogroups.com
      Asunto: Re: [gwmodel] Minimum permissible distance between bore holes in
      hard rock aquifers
      Importancia: Alta

      Dear All,

      Most of the equations of Hydrogeology and flow through aquifer have been
      developed for Isotropic homogeneous aquifer where flow conditions are
      laminar. Hard rock aquifers are Anisotropic and Heterogeneous aquifers
      and flow condition is turbulent depending on the dimension of fractures
      and fissures in Hard Rock. Thus, in hard rock aquifer there is no hard &
      fast rule to predict safe spacing.

      In Libya coastal karstic aquifer it has been observed that in some of the
      wells a pumping of 100 cum/hr produces a drawdown of 0.5 m. whereas only
      100m. distance another well a pumping of 5 cum/hr creats enough drawdown
      to dry up the well for 10 hours.

      "C. P. Kumar" <cpkumar@... <mailto:cpkumar%40yahoo.com> >
      Sent by: gwmodel@yahoogroups.com <mailto:gwmodel%40yahoogroups.com>
      11/06/2012 04:58 PM
      Please respond to
      gwmodel@yahoogroups.com <mailto:gwmodel%40yahoogroups.com>

      To
      gwmodel@yahoogroups.com <mailto:gwmodel%40yahoogroups.com>
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      Subject
      [gwmodel] Minimum permissible distance between bore holes in hard rock
      aquifers

      Define minimum permissible distance between bore holes in hard rock
      aquifers
      Tuesday, November 6, 2012 4:00 PM
      From: "nikos veranis" <nikosveranis@... <
      mailto:nikosveranis%40gmail.com> >

      Dear Mr Kumar

      I am a hydrogeologist dealing with the hard rock aquifers exploration in
      Greece.

      My question is << if you have any proposal about the minimum permissible
      distance between bore holes in hard rock aquifers.(granites, gneisses,
      amphibolites)>>

      According to the bibliography, I use the formula: R=(2,3*T*days/S)1/2 and
      in our area T range is 2-40 m2/day with geometric mean value: 8 m2/day and


      S=0,001-0,05

      Best regards

      Nikos Veranis
    • subrata halder
      Dear Mr. Veranis, Radius of Influence (R) in fissured Granite/gneisses rocks (UNESCO, 1972): 1000-1500 m (in confined aquifer)500-1000 m (in unconfined
      Message 2 of 10 , Nov 11, 2012
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        Dear Mr. Veranis,

        Radius of Influence (R) in fissured Granite/gneisses rocks (UNESCO, 1972):�1000-1500 m (in confined aquifer)500-1000 m (in unconfined aquifer)
        Therefore, safe spacing of bore holes in interconnected�fissured Granite/gneisses rocks may be maintained as follows-

        Safe Spacing (Ss) >= 2 x R >= 2000-3000 m�(in confined aquifer)� >= 1000-2000 m (in unconfined aquifer)
        If u want to calculate safe spacing precisely u have to do pumping test in bore hole intercepted�interconnected�fissured Granite/gneisses rocks �aquifer and then�
        Step 11) For unconfined aquifer�match Field Data Curve with�Boulton's type curves�2)For�leaky aquifer��match Field Data Curve with Hantush�type curve�3) For double porosity leaky confined aquifer�(involved delayed yield from block to fissures)) match�Field Data Curve with Streltsova-Adams Type curve.4)��For double porosity matrix confined aquifer�(involved delayed yield from block to fissures)) match�Field Data Curve with Bourdet-Gringarten's �Type curve.Find out Transmissivity (T) value.
        Step 2Put �T, Q, �Sw�values in Huntley's Equation (for fissured rocks) andfind coefficient �'A' :� � � � � � � � � � � � T=A(Q/Sw)1.18� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � T- Transmissivity (m2/day)� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �Q- Discharge (m3/day)� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �Sw- Drawdown (m)�� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �A- Coefficient = (2.3*log R/rw)/2πStep3�Find rad of Influence 'R' from�� � � � � � � � � A = (2.3*log R/rw)/2π� � � � � � � � � � � � � � � � � � � � � � � � � � � �
        � � � � � � � � � � � � � � � � rw - radious of bore holeStep 4Calculate Safe Spacing (Ss) >= 2 x R�
        Thanks
        Subrata Halder

        Executive Engineer (Agri-Irrigation)

        State Water Investigation Directorate

        Department of Water Resources�Investigation�&
        Development

        Govt. of West Bengal
      • asokg@tce.co.in
        Dear Subrata, Thank you for clarifying Hard Rock aquifer system so clearly. Do you have the details of reference UNESCO 1972. Was ir developed through
        Message 3 of 10 , Nov 11, 2012
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          Dear Subrata,

          Thank you for clarifying Hard Rock aquifer system so clearly. Do you
          have the details of reference UNESCO 1972. Was ir developed through
          observation or through some theoretical analysis?. If the original paper
          is available in soft I will like to have a copy of the same.Most of the
          equations in Step 1 are developed for Homogeneous isotropic aquifer. For
          double porosity I will like to know for what value(range) of porosity
          these equations are valid and what is the range of Reynold number for
          these porosity values. Huntleys equation is an Empirical Equation based
          on observation from field data. However, Huntley takes care of the
          turbulent flow part by introducing Specific Capacity ( S = AQ + BQ^n).
          Again in Step 3 we are using an Equation which is developed for Laminar
          Flow. Dr. Singhal has written a book of Hydrogeology of Fractured Rocks .
          I have not seen that book. I am sure you have gone through the book. I
          will like to know whether Dr. Singhal has included study of Anisotropic
          Aquifer Heterogeneous Aquifer with partial laminar flow and partial
          turbulent flow .



          subrata halder <shalder_2007@...>
          11/11/2012 11:56 PM

          To
          gwmodel@yahoogroups.com
          Subject
          Re: Fw: RE: [gwmodel] Minimum permissible distance between bore holes in
          hard rock aquifers

          Dear Mr. Veranis,

          Radius of Influence (R) in fissured Granite/gneisses rocks (UNESCO, 1972):

          1000-1500 m (in confined aquifer)
          500-1000 m (in unconfined aquifer)

          Therefore, safe spacing of bore holes in interconnected fissured
          Granite/gneisses rocks may be maintained as follows-

          Safe Spacing (Ss) >= 2 x R >= 2000-3000 m (in confined aquifer)
          >= 1000-2000 m (in
          unconfined aquifer)

          If u want to calculate safe spacing precisely u have to do pumping test in
          bore hole intercepted interconnected fissured Granite/gneisses rocks
          aquifer and then

          Step 1
          1) For unconfined aquifer match Field Data Curve with Boulton's type
          curves
          2)For leaky aquifer match Field Data Curve with Hantush type curve
          3) For double porosity leaky confined aquifer (involved delayed yield from
          block to fissures)) match Field Data Curve with Streltsova-Adams Type
          curve.
          4) For double porosity matrix confined aquifer (involved delayed yield
          from block to fissures)) match Field Data Curve with Bourdet-Gringarten's
          Type curve.
          Find out Transmissivity (T) value.

          Step 2
          Put T, Q, Sw values in Huntley's Equation (for fissured rocks) and
          find coefficient 'A' :
          T=A(Q/Sw)1.18
          T- Transmissivity (m2/day)
          Q- Discharge (m3/day)
          Sw- Drawdown (m)
          A- Coefficient = (2.3*log R/rw)/2π
          Step3
          Find rad of Influence 'R' from
          A = (2.3*log R/rw)/2π
          rw - radious of bore hole
          Step 4
          Calculate Safe Spacing (Ss) >= 2 x R

          Thanks

          Subrata Halder
          Executive Engineer (Agri-Irrigation)
          State Water Investigation Directorate
          Department of Water Resources Investigation & Development
          Govt. of West Bengal
        • subrata halder
          To Dr. A.K. Ghosh Dear Sir, 1) Dr. BBS Singhal has used the ref of UNESCO 1972 for rad of Influence in fissured rocks.  2) In double porosity model, best
          Message 4 of 10 , Nov 12, 2012
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            To Dr. A.K. Ghosh

            Dear Sir,

            1) Dr. BBS Singhal has used the ref of UNESCO 1972 for rad of Influence in fissured rocks. 
            2) In double porosity model, best match with type curve has been achieved with porosity=10 %. Double porosity model is more representative of uniformly fractured aquifer. 
            3) Equations in connection with pumping Test are developed based on the assumptions of homogeneous & isotropic aquifers with laminar flow during pumping...well is 100% efficient and effective diameter is the same as the diameter of the well. But in reality aquifers are heterogeneous, anisotropic with non-laminar flow during pumping...pumping well is not 100% efficient and effective dia is usually more than dia. of screen mainly, in case of unconsolidated sediments. Considering the above reality, pumping well & observation wells are installed into closely spaced & inter-connected fractures and also, nested observation wells at different depth horizon in different direction are installed to get reading of water level at different depth & in different direction and an av. T value is computed. With a view to get  as much as radial,horizontal & laminar flow pattern, pumping well should be put in lower  1/2 or 1/3 rd of aquifer thickness and Observation
            wells should be located at dist. 1.5 times the saturated thickness of interconnected fractured aquifer. Considering the above reality, Huntley used the Specific Capacity(Q/Sw) as (Q/Sw)1.18and he modifed Thiem's Eq for fractured aquifer as T=A(Q/Sw)1.18   using the coefficient A=(2.3*log R/rw)/2π  (as in Thiem's Eq.) Thus Huntley's Eq holds good for  i) small dia 100% efficient pumping well and ii) nested observation wells in different & different direction installed in closely spaced interconnected fracture zone.  Therefore, I think earlier steps may be quite O.K. for finding out Rad of Influence (R).  
            4) Dr. BBS Singhal has not included the study of Anisotropic Aquifer Heterogeneous Aquifer with partial laminar flow and partial turbulent flow in his book. 
            Thanks
            Regards
            Subrata HalderExecutive Engineer (Agri-Irrigation)
            State Water Investigation Directorate
            Department of Water Resources Investigation & Development
            Govt. of West Bengal



            --- On Mon, 12/11/12, asokg@... <asokg@...> wrote:

            From: asokg@... <asokg@...>
            Subject: Re:[gwmodel] Minimum permissible distance between bore holes in hard rock aquifers
            To: "subrata halder" <shalder_2007@...>
            Date: Monday, 12 November, 2012, 9:54 AM

            Dear Subrata,


            Thank you for clarifying Hard Rock aquifer system so clearly. Do you

            have the details of reference UNESCO 1972. Was ir developed through

            observation or through some theoretical analysis?. If the original paper

            is available in soft I will like to have a copy of the same.Most of the

            equations in Step 1 are developed for Homogeneous isotropic aquifer. For

            double porosity I will like to know for what value(range) of porosity

            these equations are valid and what is the range of Reynold number for

            these porosity values. Huntleys equation is an Empirical Equation based

            on observation from field data. However, Huntley takes care of the

            turbulent flow part by introducing Specific Capacity ( S = AQ + BQ^n).

            Again in Step 3 we are using an Equation which is developed for Laminar

            Flow. Dr. Singhal has written a book of Hydrogeology of Fractured Rocks .

            I have not seen that book. I am sure you have gone through the book. I

            will like to know whether Dr. Singhal has included study of Anisotropic

            Aquifer Heterogeneous Aquifer with partial laminar flow and partial

            turbulent flow .
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